I've recently been considering returning to Tumblr. Nothing on the Fediverse or the Freeweb/Freenet seems to really replace it. Tumblr always did have its fingers on the pulse of things, didn't it?
There really isn't anything like it. Twitter was where so many people fled to after 2018, but in so many ways it's worse than what Tumblr was like. It takes a lot to get used to the new layout of the place, but the userbase is still there.