Oh absolutely that is correct - once you've "blocked" something, you cannot then interact with it later, as it is a rather hard cutoff. I suppose you want to see something like a "remove from my feed" - basically a "hide this community from me until I want it" - rather than an actual, full-on "block". Which is notable then that e.g. a user block of an instance is even softer than that, allowing you to see and reply and receive replies from people (though you don't get notifications for those, unless they specifically tag your username). So community blocks are harder than people would like, and instance ones are softer, so they really aren't hitting the sweet spot in-between.:-)
Yes, I suppose I want that too - a "community hide" option, rather than full community block:-).