News Feed Eradicator is a must have. I can check in on Facebook for personal messages and events, even post occasionally... but I don't see the feed and I'm not the least bit tempted.

It's also good for sites like Reddit (which I'm migrating away from, of course) where you can disable it for a set amount of time, to enjoy some idle web browsing time without slipping into a vortex.

Also, not a browser extension, but I use Google's Family Link to moderate my web use. I can't access social media on my phone. My wife administers it. It's occasionally inconvenient, but on the whole it has been transformative.