I don't follow SF industry scuttlebutt too closely, but even I've heard about how An Archive Of Our Own has been nominated for a Hugo Award. And on the whole, I think it's a great thing.
I'm not normally a fan of the idea that if something pisses off the "right people", it's a good thing, if only because that smacks of the sort of revanchism we've all had too many doses of lately. But I do think about how the old-school old-guard SF fans might well be reacting to this, and I suspect their reactions are going to be annoyance to apoplexy. That tells me such people are more interested in gatekeeping and freezing SF&F as some Eternal Untouchable Thing than they are in seeing it as a product of the very people who keep it going — in other words, alive and evolving.
When I first entered what I'd call the "200-level" tier of fandom — congoing, etc. as opposed to just reading or consuming it — I got in around the late Nineties. My first con experiences were with I-CON, one of the older-school SF conventions, only just then waking up to trends like anime/manga. I didn't realize it at the time, but my negative experiences there were a direct product of the gatekeeping mentality: The real SF&F is over here; what you have Doesn't Really Count. Anime fandom was far more accepting as a whole, and I gravitated to that in short order.
I don't think such experiences are predictive of SF fandom generally, or descriptive of it as a whole. But we've all seen how the small but vocal minority of a given self-identifying group can trick everyone else into thinking it speaks for the whole.
As for fanfiction itself, I wrote some once, but quickly decided to write my own things instead. That didn't mean, though, that I thought anyone who stuck with fanfiction was somehow missing out or stunting their own growth. I came to see it as an adjunct to, say, playing Chopin on the piano at home. Not everyone who does that is obliged to practice until they reach concert-level skill. Not all of this has to be performative; a lot of it is recreational. And if there's one thing we're starving ourselves of as a society, it's recreation that isn't meant to be anything but recreation.