Are they really?
Maybe it's a sign of the times, but as an avid kiddy MMO player back when I was a child, I don't recall games like Toontown, Club Penguin, Wizard101 etc. ever having an issue with predators, nor do I have any personal stories about creepy/suspect encounters. You could attribute this to the fact none of these games allowed UGC, but even so, Roblox certainly has the resources to painstakingly vet what kind of content gets through.
Fortnite is the only modern kiddy game I really know about, but I don't think they have it as bad over there either.