Is child labor by definition exploitative? If it is then it is legal to exploit children in America, because child labor is legal in some circumstances, like a child working for a parent's small business.
It's a bit beside the point though - "child labor" is a term that the Roblox CEO brought into this discussion to defend himself, possibly because he knows it's too strong a term that doesn't really apply here. As far as I can tell the major critics used the much broader term "exploitation" (https://www.eurogamer.net/roblox-exploiting-young-game-devel...), and obviously there are many ways to exploit children that aren't child labor. The main accusation is not that they use child labor, but that they entice very young kids into making content for the game with the promise of money, but almost none of them are successful enough to actually get paid.
At Roblox, you work, they take the majority of the proceeds and then your project has to make a decent amount of money or you NEVER get paid.