I've been doxxed & threatened on 4chan[0] (most of the doxxing was actually on pastebin), I contacted 4chan admins and received no response. 4chan does little or nothing to combat doxxing & harassment, I think you're incorrect that these sites "go beyond the bare minimum legally required" at least not 4chan.
4chan does remove posts and IP bans users for posting doxx. The thing is that IP bans are easy for some to work around. And that all 4chan threads expire after some time.
If you filed abuse tickets with the companies hosting 4chan, you should be able to get some response. The kiwifarms victims are demonstrating this is possible. There is hope for you. I wish you luck.
And yet, that site is still up.
0: remnants of some archived posts https://www.google.com/search?q=%22sequoia+mcdowell%22+site%...
EDIT: nevermind what I said about the doxxing & whatnot happening years ago, apparently they're still at it as recently as January! https://archive.4plebs.org/pol/search/text/sequoia%20mcdowel...