In these cases, how are children getting in first? Where are the parents of these children??
Then, it's not the apps that create abuse, but the users on the other side. There could be a set of rules that the apps should make users agree with, and remind from time to time, like be kind, don't get angry if it doesn't work out, report strange behaviors/underage profiles/illegal stuff if you happen to detect one, ...
Is it that complicated to be adults in 2019?