tumblr is the worst designed website on the fucking planet bro
All jokes aside, I actually really love that feature. Because when I don't have a blacklist, I come across shit that pisses me off on the regular, and it always takes me by surprise, and that pisses me off worse. But when I have a blacklist, I know exactly what I'm getting into when I click that button! I'm poised to skip to the next post if it's just as annoying as I think it is. But also, there's certain words I blacklist because if they're from most people it's annoying but this one person has Cool Thoughts or a niche interest that happens to have a word that overlaps with Annoying Thing, so I want to see what they have to say. I like having the option!
tldr: putting the power back in the user's hands is almost never the wrong decision.