I think this decentralization and federation is what web3 is all about, without all the corporations calling everything to do with monkey pixel art that costs a million dollars "web3"
Federation definitely feels like the next major stepping stone of the internet's evolution. Protocols like ActivityPub and Matrix feel like a bit of a "new beginning" for communities on the internet.
Exactly. Most people have only used the Internet in its current centralized form. Not everyone had the benefit of being around in the IRC/XMPP/Icecast/BBS/Usenet/etc. days. Federated services are a new concept to many people.
I have an account, but I don't really use it much. Not because I don't like it, but because I don't have much to say really. I'm more of the lurker type.
The important thing about Matrix is to think of it like email. Homeservers are like your email provider, like Hotmail or Gmail or Protonmail. You look for a homeserver, then you just make an account on that homeserver. The "main" homeserver is matrix.org, but it's recommended not to make an account on there if you can avoid it. Remember that making accounts on these homeservers is free, so there's no reason not to make accounts on a few of them to try out.
The other thing to think about is your matrix client. This is similar to an IRC client or an email app. Luckily, this matter even less than the homeservers since you can freely switch between these anytime with basically no issues. If none catch your eye, Element is the sort of "reference implementation" so you can just try that one if you want. It has a web version too: https://app.element.io
There's some cool more advanced features like spaces and threads, but you don't have to worry about those much at first.
That's what I use Matrix for. I actually just pay for Element One and that gets me Signal, WhatsApp and Telegram all in one app (and a more convenient one than any of them). It's great and zero effort, but you can't then add your own bridges for other services. If you need them you might better hosting it yourself.