Of course advertisers, not just on Youtube, but pretty much everywhere track children's interests as well as adults. Someone said recently, "the antichrist has already arrived, and he works, in a suit and tie, in advertising" which while hyperbolic is surprisingly fitting. Mass tracking (which is a form of surveillance) for the uses of taking advantage of weaknesses in a human being (impulse control, gotchas, perceived "need", etc.) to reap monetary rewards at the expense of the individual, whether adult or adolescent, whether intelligent, or mentally handicapped... which may result in a percieved or otherwise degredation of QoL. It is immoral, not just unethical.
Most "tracking" scripts aren't age gated, most advertisers don't care, every day I grow to hate them and their institutions more and more. I would say that at this point, not having adblockers, and blocking tracking scripts is a form of enabling these parasites. Which, i believe (with strong conviction) that there is an argument to say that enabling such behavior without contest is unethical at the very least bordering on immoral.
And in the USA at least tracking children under 13 is illegal.
The real concern is determining how much or if you are being tracked through these ads. People are more aware that ads do track them but not what or how much. A larger concern is the malaise people may give when they hear this information; to put simply they don’t care. The frog is aware that the pot is getting hotter and they’re willingly asking for the man to go higher.