Lemmy UI is very easy to use, and fast too. Also, I like the concept of federation (though I have no plan in hosting one) and the fact that the community has been very welcoming so far also help with me being able to enjoy browsing Lemmy.
Of course, there's the obvious problem of lack of content but if the subreddits that I usually lurked on have fully switched to Lemmy then I would have 0 issues with fully switching to Lemmy regardless of the lack of content.