I had to do this on Reddit over the years. I have zero interest in sport, for example. And it seems there are thousands of individual communities for every sport, every team, all over the world.
I truly don’t care about them, and would like to just block - maybe via a community containing certain words? “Football” for example?
Not as of now, as far as I’m aware. You have to do it manually per instance, per magazine, and per user.
It took me a while but my /all is mostly free of the topics I don’t give two shits about. Every now and then I still have to whack-a-mole users and mags, but sadly that’s how it is.