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.
They did not. They bought postini. Before then spam was really, really bad on gmail.