It really depends on how you define “exploiting”. It doesn’t seem like you _need_ to buy the ads. A kid could make a game on any platform and would encounter similar barriers.
Would it be better if the kid played Call of Duty rather than creating something? Even if the chance to profit is low does the kid get something else out of Roblox?
To my knowledge kids aren’t dropping out of high school with hopes of being a Roblox millionaire. They may dream about it but I don’t think they act on it. I dreamed about being a pro eSports gamer in high school and I’d argue my time was much worse spent doing that.