Lemmy feels as a aplha/beta product that we ar all testing right now. Nothing wrong with that, in fact, I like Lemmy more then Reddit. But you cannot expect everyone to love it right now.
For Reddit its clear: you sign up, you search for a community and you subscribe.
Here, you sign up (if you don't get the spinning wheel). You search for a community. Oh, it is on another instance. What is a instance? Then you browse and see different Lemmy websites. You get confused, you heard something about Fediverse but what is it?
Also, there is no karma what important is for many users. Mod tools are extremly limited and all the apps you can use on mobile are in alpha/beta/in development.
There should be a easy to understand welcome page upon sign-up and I think this needs to be prioritized if we want to welcome (more) mainstream users. The post that explains how Lemmy works on c/lemmyworld doesn't cut it.