The writer is at the mercy of the muse. That's one way of putting it- emblematical, symbolical, simplistic. Another way, equally emblematical etc, is to say that each writer has a field to work in- and can only produce what that particular field is capable of producing. The soil may be suitable for grapes or it may be suitable for cabbages. No point in trying to establish a vineyard in a cabbage patch.
For instance, P.G Wodehouse was incapable of writing A La Recherche de Temps Perdu just as Proust was incapable of writing What Ho, Jeeves!
Some muses are very parsimonious, some fields are stony- and the writer has very little to work with. If they're a professional writer it means they find themselves producing the same book over and over again. It's got to be frustrating- even if the one book is a very good book.
I wonder how Jane Austen felt. Did she ever wish she was Walter Scott? Actually I think Scott may occasionally have wished he was Austen- or at least- could have added her gifts to his own. Of course greatness has nothing to do with range. Austen, I take it, is a very great writer, but no-one ever harvested so much out of such a tiny allotment.
I've written novels. They weren't published but I reckon they were publishable. They were written with sincerity but were never the sort of novel I'd dream of reading myself. So it seems the only kind of book I'm capable of writing is the kind of book that doesn't interest me very much. I know a little about frustration.
Best to stick to verse. I like my verse even if nobody else does.
I'm reading the third novel by a youngish writer who had a big success with his second- and it's not exactly a bad book but the wattage is far dimmer than that of its predecessor. He may not feel the pain but I'm getting the odd twinge on his behalf. To follow something that has the chance of becoming a minor classic with something that doesn't have a hope in hell must be galling. And of course the writer can do nothing about it. You write what you're given- what the muse hands out, what the field will produce in any given season.
Agatha Christie didn't need to write for money- except at one particular low point in her life- and during that period- when she probably didn't feel like writing at all and the muse had gone off for a wander- she produced one book she later acknowledged to be "rotten" and another she knew was "forced". She must have wished she could have scrubbed them from her bibliography but once a thing is published it's published...
I think I'm glad I'm not a professional writer. I can see why so many of them turn to drink.