I spent a huge amount of time as a kid reading and drawing and writing and just day-dreaming by myself. Probably not good training for the modern workplace with "open office" plans and whatnot, but it seemed pretty good at the time.
To this day I prefer "divide and conquer" style "collaboration" (if you can call it that), though I admit that brainstorming and debates are powerful if used judiciously (which leads me to believe that schools tended make group work out of work that shouldn't have been assigned to groups)
In a specialized environment where everyone actually cares about the subject, group work can be fantastic. This is why hackathons and similar settings are good things - everyone is there to learn, and you don't have demotivated people who are content to sit there and do diddly-shit.
In contrast, in your standard class, where most people couldn't care less, the result is that the one motivated person in the group does the bulk of the work, everyone else gives a token effort, and then educators pat themselves on the back for "facilitating peer collaboration" or whatever the ed-speak buzzword is.
Edit: The fun part is that teachers know that this is what happens, and the result is that group projects end up being hilariously easy if you get a group of kids who actually care. They're built for one person to do!
But why is collaboration THE core, such that "Everything we do, in the classroom or at home, has to be built on that foundation." ... I could argue that good collaboration is built on a solid foundation of being able to think and act for yourself.