Not sure about that one. There's a ton of minor edating/esex/grooming going on. You have massive community servers that essentially work like gaiaonline back in the day and tons of servers of 18+ communities. Horny, curious kids will always find a way so I can't blame Discord for not having a magic wand but I would be monitoring its usage if I were a parent. Only 1 of the servers I'm in is what I'd consider kid safe and it's a company's community server.
Yeah I get that it would have problems. But I'm saying that being a closed source product with staff is what allows it to fight against that.
Foss on the other hand just clones an app offers a download and calls it a day, "self host", sometimes they encrypt stuff so that not even devs or admins can see the content, they would think of this as respecting privacy, but then when they get a subpoena for a sex offender case, they can't turn up anything.