I recently created a radfem/GC tumblr account, and something interesting I noticed is that I'm getting a lot more interactions and followers for this account than my previous GC tumblr account (which I deleted a while back). And this is after not doing a whole lot besides occasionally liking/reblogging some posts. I can't say for certain, but perhaps the radfem side of Tumblr seems to be waking up, or at the very least getting more users. I don't want to get my hopes up too soon since this is very anecdotal. But if radical feminism/gender criticism activity is increasing on Tumblr of all places, that might be a good sign!
Tumblr is and has been a hub for female creativity, but female-centric fandoms have always attracted a certain type of male fan. There was the DeviantArt to Tumblr pipeline of furries. Straight up porn accounts were rampant on there and it's actually the first and only online place I ever got personally harassed.
For sure, I loved using Tumblr for creative works before I realized just how infested the place is with gender lunacy. It's definitely the best site for the kind of things I draw, Twitter, Instagram, etc can't compare.
Unfortunately, I have found that female fans can be just as bad as males when it comes to things like harassment. Just speaking from my own personal experiences, especially when to come to TiFs and their allies.