Just found this topic but I'm having trouble mentally sticking to the "this decade" part.
Honestly for me, the internet in general began to decline as soon as I noticed the rise of Wikis. Even back then I was decrying the loss of personal fansites.
I was around back in the days where, say, a single person might do a website all about the King's Quest series, or hosting stories of how their online games of Warcraft II went, or shrines to their favorite Sailor Scout.
I also remember Usenet. I remember at first thinking that the rise of internet forums was actually kinda cool.
But thing is, nowadays everything is a wiki, and individual forums really don't exist anymore, nor do services like Angelfire that let you just make your own website. Something that doubly sucks for me as I've actually thought about doing webcomics but nowadays I'm not even sure how I'd do that--most places specifically for that are designed with the attitude that you'll A) only be doing one series and B) will be doing a gag-a-day series. And anyway I don't want some overlord telling me I have to make my creations more woke (one of my comics is explicitly rather religious, so there's that).
AAAAANYWAY, just now I thought of a way this whole issue is actually kinda worse.
See at one point I was in a fandom for a specific eighties cartoon. The mods of this one forum at one point made a controversial decision that a lot of the readers took issue with. Thing is... there was another forum at the time dedicated to the exact same cartoon. You could literally just migrate.
But these days, not possible. There's only one discussion board or reddit for pretty much anything, and if you don't tow the line, tough. It's like if you wanna escape Soviet Russia but the best you can do is simply live in a hovel across the street that is exactly like the hovel you already live in and is still located in Russia.
And of course, the Wiki-dominated internet makes it easy for people to astroturf their opinions (I seem to use that word a lot lately) and act like their way of thinking is more prevalent than it really is. I imagine this is what's really going on with things like the trans advocacy--in real life almost nobody ever talks about it or they treat it like its something that only happens in other states, but to hear the internet say it, this is a big issue that will be the defining controversy of our era.
I've gotten to the point where I basically think everything on the internet is fake. If I don't see it in meatspace, it doesn't exist.