"We’ve adapted our entire culture around Facebook. That makes 'just quitting' easier said than done."
This is very true and it's actually fairly disturbing to know there are sites that require Facebook as the only way to register an account. Why would you tie your business model to a separate entity? Why would you not, at a minimum, allow normal email + password signups?
https://www.vox.com/culture/2018/3/22/17146776/delete-facebook-difficult