I just find meme communities here and there, join them, set my feed to newest, and then i start doomscrolling

But that's exactly how you would do it?

(talking about microblog fedi here, Lemmy/threadiverse is it's own thing)

don't do hashtags. hashtags (especially common ones like #memes) are overrun by repost bots and low quality garbage.

the trick is to be on a small-to-medium instance you vibe with (1k active users seems to be the sweet spot. anything larger than 2k I'd avoid. do NOT join any flagship instances like mastodon.social), follow fun people from your local timeline, and see who they boost. and follow up the boost chain until your timeline is sufficiently fun.

Search up "meme" in community search, subscribe to all the ones that interest you. Unlike 9gag, which just feeds you a stream of posts, you need to be proactive in knowing what you want and finding it. To a lesser extent, Reddit suffers from the same problem. (Though my understanding is that Reddit is becoming increasingly curated, making Reddit increasingly like 9gag in that respect). Regardless, with this type of social media, the 2 biggest ways of finding communities are to actively look for it yourself or to find out from a someone else.

It can also be a good idea to look at c/trendingcommunities@feddit.nl to keep updated on new communities