As much as I hate to say this but they are pseudo-critical infrastructure. In some parts of the world Facebook is synonymous with the internet. Here in California during the wildfires it was my experience that twitter gave better emergency notification, both from local municipalities and 'neighbors' than any other source.

As terrible as modern social media culture is, there have been positive effects on the world. Lets not forget things like the Arab Spring which might have not been possible without twitter.

Then again it helps all 'minorities' ranging from BLM to neo-nazis. I'm not sure if total net effect is positive.

It's one of those things where I don't know if the genie can be put back into the bottle. You could reset the clock I guess but it's a fairly easy service (in that there aren't many unknowns) to build back up by someone else with some VC money.

Some people use login with Facebook to authenticate their work / project / hobby sites. When you block them those will become unusable for some people.