A lot of the responses are offering an all or none response. The issue isn’t OP wants to block all memes posts, they just don’t want to see them as often.
This is an algorithm/fedi issue I suspect. It would require curation.
Since fedi isn’t really about that, the only option is to downvote.
Downvote shitty memes.
Anyone that was around while Reddit was growing will remember that there were few subreddits to begin with. I think fediverse needs that to happen before expanding.
I don’t know how to fix it. Maybe sub-feddits need to be pruned if they aren’t thriving. Maybe tags in titles would be more helpful until they have enough content to warrant their on category.