In which case we should ban children from using game consoles, computers, cell phones, ISPs, TVs, or anything that else that comes with a ToS/AUP/T&C
How enforceable all of that is legally would be up to the courts, but that's true for social media sites too. If a 15 year old signs up for a social media site they're forced to agree to terms that might not hold up in a courtroom. None of that protects the child from having their data harvested, sold, and used against them for the rest of their lives.
If we agree to ban kids from using social media on the basis of them not being able to legally enter into a contract, we'll have to ban kids from a whole lot more that social media since so many things in our lives require one. Even things explicitly made for children.
That sounds pretty good. Maybe companies targeting their products and services at children shouldn't attempt to enter illegal contracts with them?