I've been an on and off player since 2013? Depends on what you mean by crumble. I'd say a variety of 3 things lead to this last year.
1. Little content early in the year, nightwaves don't feel like contnent at all.
2 . Old Blood and Emperyean being broken and both insanely grindy. I love grind, but it's gotta be worth it. If I'm spending more time than ever before, I need a reward that's use matches that. Old Blood at least occasionally gave some awesome weapons, Emperyean gave ships with mostly crappy features, that didn't feel like rewards when playing most of the game.
3 . I'd really like your opinion on. You said the community was part of the problem I believe? I'd love to know how, it seems like DE not listening to the community, then occasionally adding very simple fixes years down the road, not acknowledging it should have been done sooner or that players really wanted it. I'd say the worst the community has done is not call out people with very poorly or maliciously reasoned arguments.
What really put Warframe being in a bad spot in perspective was Anthem. Last year they had so much confidence making fun of them, now they have openly admitted every update since has been received poorly. Most of which took place before Covid19, which means it was started and worked on well before Covid19.
Side note, I haven't played SS, have next to no desire. I liked the weapons from old Blood, ships were hardly fun and a grind beyond belief. I had been playing nightwaves 1 and 2 alot because I wanted to play, didn't need content really. But with those disappointing updates combined with the feeling of possible impending doom due to the reworks of melee and dmg types( which don't seem to be good or bad to me get) I just kind of stopped.