Google pretty much undeniably has the best ML people in the world and I see nonstop hate at YouTube for their automated filters false-positives so I don't think it is an easy problem.
It seems like the only way to profitably scale this type of service to millions to a billion users, so it ends up being the go-to technical excuse for the people that think our moral standards should budge for the technical feasibility of maintaining these insanely large social media setups, like it's some sort of inherent right to be able to do that and turn a profit.
In a perfect world, where everyone is liable for the material they host on their own servers, services with this many users wouldn't exist in the first place.
The usage of AI as a magic silver bullet always frustrates me.