I've seen and even tried to run a few polls on age (mostly on mastodon and microblogs).

The age demographic of the fediverse definitely leans as you think ... on average ... Xennial tech/academia/nerd oriented. Not too sure linux users are too dominant though.

As for more diverse users? This isn't mainstream (yet?). There's a lot of inertia around the big-social era. It lasted for a long time relative to the history of the internet, ~2008-2022, ~14 years, which is nearly as long as the internet had been around for before then. So many are stuck in their ways and stuck on the idea that there's only one or two places to be online and they're on one of them, the "right place". I saw someone on twitter just yesterday say that they'll stay on twitter until it goes down and then never go anywhere else because they don't want to bother with another social media platform.

It seems that the idea of a monopolised internet is breaking apart and fracturing now, which is a good thing, but not completely good across the board. Where for instance should emergency information be broadcast? Previously I would have checked twitter before mastodon without blinking. Now, Lemmy might actually be pretty good for this (only realising this now as I write). So there's also a dimension of kinda believing in the big/monopolised social media. This is likely more prevalent amongst younger people, from whom, for example, I've heard ideas like that decentralisation is some weird tech-libertarian ideology and that the "town square" is actually a good thing and something that should be committed to. As far as anyone that has any commercial interest in their social media profile like businesses (both small and big!) or journalists, not being the town square, and the lack of apparent "engagement" and "virality" on the fediverse is definitely a turn off. And of course having those types on a platform naturally attracts others. All of which is not to mention that the decentralisation thing is something your average person just doesn't have the time or patience for and the insistence of some of the people on the fediverse that you should learn about it and that it isn't hard are off-putting to some.

In the end, we've reached a bit of an impasse it seems, where we've culturally outgrown the idea of an important service like our online existence being at the mercy of private corporate whims, but don't have a clear way out. Accepting that the internet is diverse and not monopolised may just take some time.

Where the fediverse comes in is that it gives you both a fractured and diverse social media space but also the ability to connect anything to anything with a standardised protocol. It's a powerful idea, just like that of the internet itself, and whether it's activity pub or some other standardised protocol, I hope it makes it.