I think Tumblr's like reddit in that parts of it are cesspools whereas most other parts are fine. (I've
been on tumblr for years and have very rarely come across the teenage demisexual "sjw" types, since I don't follow such people-- so those posts don't appear on my dashboard. You have to be actively seeking them out to see them in my experience. And now there's lots of blatantly satirical ~sjw~ blogs that some people still think are real). There's medieval bestiary tumblrs, various nerdy special-interest tumblrs (and a huge amount of BDSM porn for whatever reason) and lots of fantastic art/photography tumblrs so it just depends on what you're looking for really. It's a good blogging platform for the lazy.
Interestingly, I actually run across "anti-sjw" types a lot, and it seems like half of them are 18-year-old furries with anime avatars who use My Little Pony quotes in serious discussions. So maybe teenagers are just getting stranger and more insufferable in general? (Then again the whole otherkin thing has been around quite a while now-- over 10 years at this point)
...And now I'm suddenly having flashbacks to the AOL message boards of the early 2000s. God those were some unsettling places. (And the chatrooms that always seemed inexplicably filled with foot fetishists, etc)