The default lemmy UI is... not great
It reassembles the new reddit UI and that's not great. It has a lot of wasted whitespace on ultrawhide monitors.
Kbin's UI is a lot better and it reassembles the old reddit UI, in a modern way, I like that.

With that said, I'm a huge fan of federation, and want to support it, but I'm aware things aren't great right now
Discoverabily is not great, and I had trouble finding subs I care about... as a power user... imagine normal users doing that...

Just like with Mastodon, the main Lemmy website has a bunch of technical jargon that will scare any new user away immediately.