This is a really good thread and a really valuable discussion—valuable enough for me to stop lurking and make a post.
Like others, I have also been around for awhile, mainly as a veteran lurker. I think I had my first FF account in 2002 or 2003. I think I missed the heyday of Dimensions but I have fond memories of the story archive. Still talk to a guy I met through Bellybuilders a long time ago when I was first exploring my interest in fat men (as an admirer and feedee). I can't say I've "seen it all" but I have seen enough over a long enough period of time to notice some trends.
I think the broad thrust of the OP's point is true—lots of things are getting worse as far as interpersonal entitlement and exploitation go, increasingly extreme and reckless content, etc. And I think Munchies makes a lot of excellent points that this reflects not only the perils of patriarchal heterosexism in sexualized spaces but also broader sociopolitical trends. Material conditions are deteriorating, the world is on fire, and at a collective level we're going through a mental health crisis exacerbated by the trauma of the pandemic and the isolating and commodifying dynamics of digitizing every aspect of our lives.
I've been thinking about this a lot in the context of the increasing prevalence of overt 'death feedist' content. This is really something I've only seen emerge in the last few years—I think 2017 is when I first started really noticing it on Tumblr (one of the better feedist spaces online if you are queer or at all thoughtful about kink... and don't mind wading through a lot of garbage accounts and terrible site design to curate a good dashboard).
Obviously the extreme, sadomasochistic edge of the kink has always been around, but definitely never as openly as it is at present. This is admittedly speculative on my part but I think there are several reasons for this:
a) the generalized nihilism borne from the whole "world is on fire" thing as it manifests for feedists—no future! who cares! gorge recklessly!;

to the extent that kink often works as a way of metabolizing shame, taboo, and trauma, it represents the way the unhinged fatphobia of "obesity epidemic" discourse is incorporated into sadomasochistic fantasy for people impacted by it during their psychosexually formative years;
c) the nature of sexual desire generally and pornography in particular is that its satisfaction is always bound to novelty and excess... which means it can never be fully satisfied, and given the imperative of instant (and endless) gratification it can only ever escalate.
In feedist circles this manifests in bigger bodies, faster gains, extreme stuffings, sexualizing health problems, etc, but I think this trend is can be observed in other niches too: progressively 'harder' scenes are required to get off. (IMO David Cronenberg's "Crash" [1996]—about a group of people who fetishize car accidents—is the best depiction of this dynamic put to film.)
I mention all this because I think it underscores that there is something endogenous to human sexuality that drives it towards finding and smashing limits. Negotiating the tension between sexual fantasy and reality is the work of a lifetime and requires a lot of maturity. This is true even for more 'conventional' sexuality but especially for anything unconventional, where most of us are still so bound by shame that we can barely articulate our desires to ourselves—let alone share them with others—so we have to learn the hard way about separating fantasy from reality and not treating human beings as sexual objects. This is also complicated by the proliferation and accessibility of pornography, and the parasocial relationships people form to content creators—which is probably the only medium a lot of (lonely, poorly socialized, etc etc) young people have for expressing or satisfying their authentic sexuality. Throw in the additional layer of cisheterosexist fatphobia on top of all this and I think it explains a lot of the really toxic behaviour we see in the community these days.
But I don't necessarily think it's uniformly getting worse. For instance, I also see a lot more really thoughtful discussions of these issues in the community from a fat liberation lens, particularly among Millennial and Gen Z queer and trans feedists on Tumblr. Even the quality of discussion in the FF forums lately is leaps and bounds ahead of where it was a few years ago. In a lot of ways I think the problems we are noting here represent the inevitable growing pains of a community finding increased visibility (if not acceptance) as body positivity becomes more mainstream. And we're all here because we love growth, ya?
There has always been a tension between people who see feedism as just a way to get off (and/or make money) and people who see it as a lifestyle—a way of orienting existence in the world. We're seeing that play out now in the cultural conditions of the