Or just don’t follow anyone there? Nobody is forcing you to read posts on any federated instance. I am shocked by the kind of egocentrism that leads you to think that if you don’t like people on a given instance, you should prevent everyone else on your instance from interacting with them.
No, tumblr is terrible in a 'hyperventilating gaslighting cliques of pretentious elitist malignant narcissists acting like cult leaders and followers' way.
Tumblr on fediverse by default will increase variation of community in fediverse. Especially, fediverse right now is still mainly filled with American or European related topics.
In the early-to-mid 2010s Tumblr was mainly associated with "social justice" types of people, it seems to have become a lot less relevant at some point in the late 2010s.