I'm on discord but not for the sociability so much. However, there are some hyper specific subjects that get served up there. Personally, I find it very chaotic.

There's a learning curve with using federated platforms wether it's Lemmy, kbin or Mastodon. Things will definitely improve as these platforms get more fleshed out but as is, it'll probably come off confusing to a casual user.

To give Reddit and Twitter credit, they made it convenient to join communities as you just need a single account to interact with hundreds of thousands of communities and millions of people. It's convenient as a user that you only need one account as opposed to 30.

If anything, we might end up reverting back to using smaller forums until the fediverse has time to catch up. I think it's unsustainable as a business model and we're seeing this with the self-destruction of both Reddit and Twitter where they're leaning too far to try and make a profit where it's affecting user choice and experience. Most people that ran web forums back in the day didn't do it for the money but instead they wanted to foster a community. Yes going back to that might cause the internet to get a bit more fragmented, but I think it'll work out for the best as both forums and the fediverse puts users first.