Lemmy has the same discoverability and usability problems as Mastodon. Especially for non-technical users, there's too much friction required to find their communities and aggregate them into a single usable feed with a nice client. And that's assuming they can even conceptualize what the fediverse is.
I'm a technical user, and I closed join-lemmy.org after ten seconds because it was too many clicks to get to an interface that looked like Reddit. I did manage to find a community by clicking "join," and arbitrarily picking one of the communities on the page (which were presented in random order on every page load). I was disoriented and didn't know what this community was - did I land on the equivalent of a subreddit? Or is this a federated instance that includes all "subreddits" the server is connected to? Then I saw an intimidating user interface with sparse activity and low numbers of comments. So I concluded that if that's how I felt as a technically sophisticated user, then Lemmy doesn't stand a chance of gaining traction with the average redditor. I went back to Reddit and noticed most of the subs I like are done with their blackout.
Lemmy can succeed, but it needs a usable client that abstracts away the complexity of federation and choosing which servers to join. It seems like a perfect opportunity for Apollo, RIF, and the other award winning Reddit clients that are about to shut down. Why not port their apps to point to Lemmy backend(s) instead of Reddit? They could bring their loyal userbase to Lemmy, solving the chicken-and-egg problem and helping to bootstrap activity. And they can keep their UI, solving the problem of the intimidating user interface that would otherwise inhibit adoption of Lemmy.
It seems like there is a relatively straight-forward path to integration, but the opportunity window is probably closing soon. They'd need to act fast. The first step would probably be for Lemmy contributors to build an open source interopability layer that implements the Reddit API (maybe this already exists?), and for the client apps to figure out how to add one more layer of indirection to their interface ("servers").