I think you may have misunderstood. I have FOUND communities, but there is not much engagement or activity. I have resorted to discord channels for most of them, but it is not the same.
Some of my most active subreddits were different 3d printing and 3d modeling groups, groups for games like Overwatch, and Payday. Different AI focused groups, but specifically groups like the Stable Diffusion sub, Subreddits that discuss my favorite shows, or styles of music. None of that is active here. It isn’t that they don’t exist on Lemmy, they are just ghost towns. I joined multiple instances and am very active and engaged on multiple accounts, on some of these groups - but there is not response. I was in the top 3% of karma earners on Reddit - and I did that by submitting and commenting a lot. That just doesn’t happen here (yet).