I do like a lot of things about Kbin, and visually it's much better than unmodified Lemmy in a browser, but it also has its own share of problems, not least with intuitiveness. I don't understand why communities are called Magazines, and the terminology of "Favorite", "Reduce" and "Boost" are very confusing to me. Trying to make a new thread might lead you down a microblogging path instead since "Post" sounds more like a new thread than "Article" to a newcomer.

There also seems to be much slower sync between Kbin and various Lemmy instances compared to intra-sync between lemmy instances themselves. Kbin also doesn't have an API (yet?), but a more tech savvy individual than me will have to say how big of a deal that is.

Both Sync and Boost have large and loyal userbases and will probably attract plenty of users to Lemmy, and good Third Party Apps might help with first impressions and onboarding for new users.

Ultimately though, content is king. I liked Kbin better when I first made my accounts, but then we had a Race Week in Formula 1 and the community here was dead while discussions were happening on Lemmy, and since the sync was slow so I ended up over there.