I don’t think federation has to be an obstacle for non-tech people. They don’t really have to know about it, and it can be something they learn about later. I really don’t know if federation stops people from trying it out. Don’t people think, “I don’t know what instance to join, so I’m not going to choose any?”
Personally, having no algorithm for your home feed is what I don’t like about it. Everything is chronological. Some people I follow post many times a day, some post once per month, some post stuff I’m extremely interested in sporadically, followed by a sea of random posts. Hashtag search and follow is also less useful because there’s no option for an algo.
The UI seems fine to me. I guess I’m not picky about UIs. The one nitpick I have is on mobile, tapping an image will just full-screen the image instead of opening the thread.
I remember liking Opposing Force and Blue Shift too.