Some subs/instances simply don’t exist, or don’t exist on a usable scale outside of reddit. Try and find things on lemmy about yoyo’s, for instance. It doesn’t exist, and if it did it would be insanely small right now. But on reddit r/throwers is a yoyo sub with like 40,000 members.
Lemmy is all well and good for big stuff and general info and more mainstream things, but there’s a lot it still simply doesn’t have the user base for, yet.