We do need and have a goal. As a taxpayer I'm paying for school for kids other than my own. If there is no goal of that, then I am wasting my money: give me that back so I can go on vacation. Let those kids play in a park or whatever instead of spending time in school.
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.