As someone who is still on reddit and other mainstream sites as well as fediverse, here are my impressions.
There is definitely a frustration around the enshitefication of most of the major platforms, which is causing users to seek out alternatives to these sites. A lot of this has translated into increased traffic and membership on fediverse sites like Lemmy and Mastodon, but the reality is the situation still hasn't gotten bad enough for most general users to abandon the platforms entirely, or they stick around because despite everything, they are still the platforms with the most reach, and are still easy to use for most users.
Mastodon seems to have waves of activity based on the latest major fuckup by Elon Musk, but because of the learning curb and the differences in how Mastodon works, combined with the lack of user activity compared to twitter, most users don't stick around. Meanwhile, Bluesky is advertising itself as twitter pre enshitefication, and Threads is promising a userbase comparable to twitter without it being ran by Musk, which to a more casual person may seems more appealing. Fediverse is more appealing to people like you and me because we're nerds. Like we are interested in the technology, and want to dive into it to create the web experience we want. That's not going to appeal to the average user though.
There are weeks where I spend most of my time online on kbin and mastodon, and if I go by word and news posted, it would seem like reddit and twitter are on their final ropes, everyone is rushing to the fediverse, and we are about to enter another wild west period of the internet. But then I go back to reddit, and most of the communities I was apart of still seem as active as they have ever been. Most people I followed on twitter still post regularly with similar amounts of likes, retweets and comments, and most content creators will still point people towards these platforms for further engagement.
One space I have seen a major shift in is the LGBTQ community. There is definitely a diminishing of activity on major platforms mostly because the recent enshitefications have made these platforms more hostile places. Fediverse is a popular alternative for these communities, which is probably why you see a large amount of queer users within the fediverse. A lot of tech communities have also flocked to the fediverse and other communities because these spaces attract a lot of tech savy nerds, and are a great place to find fellow techies who know what you're talking about.
Overall, There is definitely a shift in how people use the internet and how they interact in Social media. The echochambers within the fediverse though would make it seem like it is bigger than it actually is. I would say we are seeing the dawn of the expansion of the internet, where instead of everything being centralized on 4 or 5 major sites, there will be a number of smaller sites that host their own communities. It probably won't be anywhere near as decentralized as the pre youtube and facebook era of the internet, but you'll at least have other places to go to when you get sick of a site, but still want to find like minded people to discuss your interests with.