Sometimes the only solution is simply to avoid a platform altogether, or ruthlessly limit exposure, as you say. All the stuff I described in my post is minor tweaks, really, and if that doesn't block out the stuff you find most distressing, leaving is the only option. I can't control how other people use e.g. Facebook, and if muting and blocking doesn't work (and I don't want to unfriend them), I would have to leave (which is basically what's happened with Twitter).

I'm friends with real-life and online friends and family on Instagram, but I'd say they're only about half the accounts I follow. Thankfully they all seem to use Instagram in much the way I do — sharing calming/soothing/beautiful things.

I agree with you about Tumblr; I left several years ago and it was such a weight off my shoulders!