To me that award goes to Twitter, not Facebook. Facebook is actually useful to stay in touch with friends and family in a private fashion. Twitter on the other hand is constant pettiness, aggressiveness and bickering 24/7 from people looking for validation and internet points. The worst internet mobs came out of Twitter and my statement doesn't discriminate between political sides.
Twitter is just a platform for idiots to yell at each other and marketers to sell their books/wares. However I haven't noticed people spend HOURS on twitter, like I have with facebook. Facebook is much much more insidious and poisonous.
At least messages are still E2E encrypted. If you avoid all other facebook systems and restrict the apps permissions I think the damage can be contained to a decent level.