In Memmy, go to the community, under the menu is an option to Block Community. It’s kind of an endless game of whack-a-mole. My all feed has improved, but every day there’s a few more I have to block. I like to check All occasionally to get of my bubble but it’s a bit of a mess.
Not that Reddit’s All feed is any good right now, which is at its absolute lowest quality I’ve seen in over a decade. Resembles instagram more than what used to be Reddit.