I don't really get why you need to block communities. I block users but that is because they comment and post about communism on every single community. Luckily there are only a handful of users who do this.
I do wish Lemmy was a little more politically neutral. I just try to ignore the political stuff. I also choose a instance that isn't focused on politics.
why? because you don't want to see certain things in your feed. people come hwre for various things. some people come here to mentally relax, so they don't want to hear about negative topics like wars or people Fighting all the time. other people just are not interested in certain topics or posts but have them flood their feed.
example: i come here for relaxing mentally and to see posts about topics I'm interested in. so I don't want to see negative stuff like causalities in wars, hearing people complain what bad things they experienced this day, what stuff has gone wrong in their life and other negative stuff. another example is lemmynsfw where I don't want to see males showing their genitals to me since I'm interested in women, not guys. so i block communitys who are about such things.
short: because people don't want ro see certain stuff. that's why there is a block function. lemmy without a block function wouldn't be useable since you get flooded with tons of posts you aren't interested in by default without any blocks.
I personally just don't subscribe to communities overrun by communists. I am not saying the ability to block communities is bad, I just don't use it myself