We should remember that a lot of these services are still young, and definitely did not expect the popularity they got. I know they’re all working on scaling up and adding features, but the teams aren’t huge and they’re playing catchup with established sites (not that Reddit was ever great at moderation.)
Heck, running a Discord server wasn’t all roses. You take a month off and you come back to find a moderator has alienated most of the community by abusing the community rules. So yeah, building the framework AND trying to moderate has to be overwhelming.