The biggest issue is discoverability. There's not federated way of linking to posts or comments and it's really hard to find the content that's there.

For example, if you subscribe to one of the bigger meme communities, your feed will be 95% memes and it drowns out everything else. But if you unsubscribe, you get 0% memes. So it's virtually impossible to get like ~20% memes.

The hot and active sortings, which should help you find worthwhile content are far too stable. They only push the same stuff over and over. Good new stuff often gets burried, because it doesn't have enough engagement to make it into hot/active which would provide engagement, while the stuff that's already there stays there.

Search is another big issue. On Reddit, if I read a post before, I could just search for it and find the post quite quickly. On Lemmy this hardly works at all.

Reddit's SEO is also really good, Lemmy's doesn't exist.

Other than that, it's a nice place. Discussions are civilized. I miss a lot of the more niche content, but maybe it will happen in the future.