The problem with that style of blocking is that it goes both ways.
Someone can post ignorant shite and block anyone who would give them pushback, then when other people look at the comments they think "wow I guess everyone here just agrees with this".
I guess I've always viewed making a post as standing on a street corner and shouting, not meeting on the side of a street with a group of your friends.
I guess it depends on if you view "subreddits" as communities, that is groups of people that you choose to associate with if you post there, or if you view them as topics that you want your post tagged as. A lot of social media sites take the latter approach, but reddit used to take the former, as did old style forums. It might just be from me spending more time on those kinds of platforms, but I do think the "community" approach is better.
Star Wars is Dune for people that love WWII and samurai movies.
Dune is the Foundation series for people that like mushrooms more than math and have weird ideas about women fueled by angst over their wife divorcing them.