At a certain level of daily MAU, (say 100k?), every single post most be manually checked before becoming available to the public. They should be checked for a) child porn b) violence c) doxxing

They are free to run algos to auto reject, sort whatever order.

This would likely be too burdensome, and the socials would almost certainly have to start charging for access, which in of itself would probably remove much of the problem.