I completely agree. If I wanted anything from current schooling it would be giving students more abilities to develop themselves. Obviously that doesn't mean a 16 year old playing videogames for 12 hours a day, but students who like doing sports should be doing much more of it and those who like learning should be doing much more of that and so on.
Kids learning how to develop themselves is a good thing ONLY if they choose the "right thing" to develop. You can get really good at video games, but as you already said probably not a good only investment (a fine hobby, but keep it a limited time hobby). There are some sports that because of injuries should really be banned (but I won't list them because as soon as I do there will be a lot screaming from people who live that sport). What we need is kids who develop themselves into something that makes them good productive adults - for some jobs we need adults to do this is boring and so kids won't do it unless forced.
The goal is wide and open ended, but there is a goal. Likely others can word it better than me, but it goes something like this: "to produce kids that grow up to be productive adults that contribute to society and make the world a better place."
We all are not the same, and even if we were there are many different needs. I need someone to haul my trash to the wherever it is handled, but my city only needs a few hundred such people (thousand?). A few other people need to ensure I have clean water. A lot of people need to ensure I have food. Some of them need to provide medical care. Thus we need to have multiple different outcomes (if you are just hauling trash you need less education than the medical doctors, while the person designing the dump needs more education than a basic nurse).
Because of the different needs in society there will and must be debate over what the curriculum should be. There is no way to teach everything. Time spend teaching one subject is time that cannot be used for a different one. There are many different ideas how to teach, and we need better science to figure out what really works.
What can I say; I like arguing. We don't actually have to choose a single goal - everyone can have different goals. If schooling isn't compulsory then you could have a mass of different people doing different things for different reasons and it all gets called 'schooling'.
If schooling is state managed ... the same interest groups exist, they just have to fight over the curriculum in parliament or the Department of Schooling. The end result will be a weird hodge-podge of compromises that nobody can confidently say satisfies them completely and doesn't have a clear goal.
It happens that we cannot say that there is a goal of schooling. Some people may have one goal, but other people may have alternative goals. There are some really tricky edge cases, like History - should Mongolian schoolchildren be taught that Ghengis Khan was a hero, a scumbag, a disaster, a triumph, a fact, a national symbol or someone best forgotten? That is not a question where a reliable and enduring consensus can be reached because real life is too complicated to take a final universal stand on something that happened 1,000 years ago.