I haven't deleted my account yet but I very rarely visit Reddit anymore.
There are a couple things about Reddit I miss that Lemmy lacks at this point, such as r/askhistorians or r/whatisthisthing which could be useful. I don't think Lemmy/kbin/the fediverse are widely adopted for me to get a reasonable answer to a question like "what is the oldest practical warning sign known to exist?"
Discussion boards of things like Battletech or Satisfactory or other slightly niche interests exist here, but are pretty much inactive.