This used to be a sensitive topic for me when I held myself to "higher standards" — basically, I wouldn't have liked my answer a few months ago because my goal was to become a srs bsnss writer, and I thought approaching roleplaying with the mindset of a writer was "unhealthy."
I can say with confidence now that I'm 100% the former — I have always sought to put genuine polish into every one of my posts. I don't treat each one like a published work; I've only edited or revised posts after they've gone up for the hell of it, as practice. But I don't just "put down" words. I focus on syntax, and on conveying tone, and I guess portraying a distinct voice, too.
There's a lot of benefit of making your posts "enjoyable," sort of like stand-alone short stories if you went back and wanted to polish them. Because, if you want to, there are your portfolio pieces! There's that short fiction! There are those ideas that you made happen like it was effortless! Roleplaying not only gets you writing, it gives you something to show, future pieces that you can go back and polish. Every new post is a writing exercise! The hard part of writing for me, anyway, is actually writing, not the editing, so having stuff ready is invaluable.
Roleplaying has always been a motivation boost for me, I've realized. Going into a blank document or empty sheet of paper with the intention of writing any semblance of sci-fi would normally scare the shit out of me. But my app for Ice's new RP has, like, a 5 to 6 paragraph origin story about interplanetary conflict, and it may have holes in its premise, but it's better than not writing it all. It honestly didn't feel hard to write either. Roleplaying just gets me to express things I never would have.
As a disclaimer, roleplaying doesn't replace solo-writing. The latter is where you genuinely develop, I think. For example, I would better grasp my voice with more emphasis on writing independently. Also, approaching every post more "literary-conscious" does not mean your posts (LOL my posts) will be well-written. But I like having shit, being able to write something and say, "Wow, I wrote that, and it wasn't even that bad." I guess it would feel like an empty hobby to me otherwise? But we all get something different from it.
(Figured no one else would write a long-ass reply lmao)