I guess for the left it's the problem of sticking religiously to pamphlets some person in some long past (or current) age has written, the one flavor as well as the other.
The center part is totally obsessed with its "human rights" babbling and all of the things which are holy to them and which they are never going to break or reform or change under whatever circumstances and hardships they have to exist, even if their lives would depend on it - mostly these guidelines are from long past decades and centuries whose circumstances and systematics are all not true anymore, or at least way more complex.
The radical part is obsessed with the writings of its pioneers too - whether be that with stuff from a more current age that nearly completely ignores history and just paints everything in the colors that the indoctrinated mind wants to apply (Identity Politics), or be that it hangs on every word of Marx and maybe even Lenin, and creating practice that works and which doesn't involve making half of the world convert to their worldview is all not their discipline.
Both flavors (and probably all others of that direction) share a similar problem: Get away from your mentors, pick out whatever you want from their writings which you see an important lesson, and go to create concepts that can be lived by people even if they don't share all of your beliefs.
The right side of politics has one deciding advantage in this: They aren't too proud to pretend on the outside that they can become a little more modernized, accept alternations to their concepts, while actually remaining the same thing like before in the background. They accept to do whatever it takes to win as much people as can be over for their worldview and policies. Maybe resulting from a background that is like "when I pretend to God to accept something that his writings don't allow, well, he'll have the mercy to turn a blind eye this time, doesn't he?", conservatism learned that some modern paint job doesn't mean the end of the world for its concept. It's not essential to control ALL of peoples' thoughts and behavior patterns, only the most important ones.
Leftism still has a problem to learn that, and the fact that today only the Western interpretations of leftism are spread throughout the world doesn't make the matter any better 'cause Western leftism mostly orginates in the ideologies circulating round on American university campuses, which are deeply enriched with the dogmatism of the Puritanism that shapes American culture until today.
So, in other words: Leftism through thinking and making conclusions exists way less than dogmatic "leftism" which is actually only another version of Puritanism, which only campaigns for different things today within the context frame of "we're the one and only true path and all others are heretics destined to end in hell". Today it's only something else than "work the hardest all your life to see if you're one of God's chosen ones" in order to stay true to the path.
And so it is what the bigger picture shows...
(Ah, sorry for the length...)
It's interesting how you link left-wing politics to puritanism.
The republicans in the English Civil war were also- many of them- puritans- some of them extremely radical in both politics and religion. Historically two things seem to go together. Someone once remarked that the British Labour Party owed at least as much to Methodism as it did to Marx.
The American versions of "leftism" which have spread throughout the world are tainted with Puritanism as it is a very base of America itself. Many other things too!
The dogmatism the radical feminism and Identity Politics show in how they view and judge things - this is all something, if you compare it to the dogmatism of Puritanism, as well as its constant playing with guilt and threat of the wrath of God if humans don't fulfill its rules 110%, these things you also find in there.
If you don't do this or that, don't vow your oath to this or that, then you are an evil whatever-ist and social shame is brought upon you in an aggressive way like people once were talking about the merciless urge of God to punish people if they don't follow all of his rules.
European leftism, at least as I find it, also must let the question be put to itself how much the Lutheran working morale had an influence on them, I think. Or, maybe also to say: How much still they were and are unable to overcome it, to not follow it so strictly - how much they are unable to recognize or ignore that this component left a footprint in their ideology too.
I mean it in that way: European leftism, or maybe even only Central European leftism (?), has quite an obsession with working hard every day and getting it into peoples' heads "if you don't work, you're worthless". They have quite an obsesstion with "I am what my hands can do" - if their hands can do nothing or can't do anything anymore, they suddenly fall into a black hole, into a big void of themselves.
Takes way too much space in the head than it should, in my opinion.
(This is difficult to bring upon the table as European leftism is very strongly intertwined with the idea of atheism - and, think fo yourself, what it would mean to it to admit "no, we aren't completely free from the cultural norms that church laid the base for before"...)
In general, I'm pissed off by the dogmatism that all fractions in this openly show. All the time they're talking about their prophecy that already started with Marx or they're constantly busy with stating "no, we can't do this because this undermines human dignity! this can't be negotiated!".
You stand there as an innocent bystander always and think for yourself "well, so then what CAN be negotiated? what have you got to offer to do instead?". It seems like nobody ever really racked its brain about what they plan to do instead, if all which other fractions offer or put on the table is a no-no. Or as if it was so that they firmly know their instead-concept would be a total bunch of bullshit (that couldn't even get near to the comfortabilities which the system of the current ruling class can offer people, even under the worst conditions)...
The British Labour movement is strongly imbued with The Protestant work ethic- to the extent that people feel it's not just disabling but shameful to be out of work.
Oddly enough the ruling classes have never felt diminished by not having "proper jobs"- in fact rather the reverse.
Same thing I hear through when other people talk about GDR communism.
It's just... well, I know, there's been a lot of shit done during the time of the turnaround here, but, on the other hand, I can't call it a good thing if masses of people, losing their jobs, suddenly fall into a black hole mentally. Something's really freaking gone wrong with that in that case.
This tells me that people learned the motto "my job is my life" even though.
First, this is no better than capitalism reducing you to what your hands can do and throwing you away as soon as you're not quick enough in that anymore. When work is life, then your character starts to vanish the same way like under that rule. Doesn't matter if the working conditions were way more comfortable then...
Second, you can do that in a post-war time episode where all just have to rebuild the world around them and get back to the state of life quality as before the war as quick as they can. But, as soon as the world is rebuild, you managed to acquire one or the other luxury item for yourself, what the heck is this for? Not for your people, but for feeding the capitalists only in order to get a little bit of foreign currency here and there to go on living. This is a machine destroying human lives and the environment no better than capitalism 'cause you fucking run like a hamster in a wheel - and in the end this effort won't be enough 'cause the capitalism you have to make your deals with in the world economy is planning on letting you starve on the long leash anyway.
And third, this leaves no place either for all people who haven't been taught anything useful by their parents or by the system, who don't want to or who are too sick to deliver, as well as it disregards the fact that you can't do the same "Produce, produce, produce!" economy that tries to take over itself in a world where there's a growing larger mass of people than actual jobs to do.
You don't need people to define their personal value as a creature by their jobs and skills in a world that soon enough has more people to share the work among all of them so ALL have any bit of work or job to do at all.
Protestant work ethic (you brought me upon the correct term again) is based on a mindset where there is always a world to expand to either, where there is always a world with arising needs to be covered (in the case of supply of services, foods, water and energy this is correct) and so there is no reason to stop working hard every day.
But, Protestant working ethics are a thing from the end of the Middle Ages... Where people still got 7 kids in order to make 2 survive until they're adults, where people died from trivial diseases because antibiotics weren't yet discovered, where people didn't grow too old, industrialized agriculture didn't exist and where they didn't have that huge a hunger for electricity to run light, computers, phones and TVs in their homes.
Additionally, a lot of work was done by manual labor, assistance through animal power at best. A lot of those things produced were able to rot naturally in foreseeable time, so producing new ones wasn't that much a deal of exploiting nature and destroying it.
This situation is no more, has become very different with the industrialization... You can produce tons of corn, that which is left then not eaten rots and returns to the soil, but you can't produce tons of plastic only because your work moral says you're worth nothing if you don't produce a ton more each year or if those capitalists you have to make your deals with demand a ton of plastic more each year (because it's so cheap for them to buy it from you).
I don't know why people don't see that far themselves - if it's just romantisizing or, plain to say, the stupidity of an average human brain that can't think farer than his own doorstep.
Often the latter feels to me like this - people absorbed by the rightness of what happens in their world, privately as well as by the ongoins in human civilization. The stupid "crown of creation"-nonsense, but without speaking about it loudly or even being aware of it.