Yes, feedback is hugely essential. It's more of a question whether feedback should come as an impersonal mark on a paper that provides minimal direction, or if it should come from a person who knows your unique strengths/weaknesses and can direct you in a way that will help you thrive.
As for SAT/GPA, they are terrible indicators of an individual's effectiveness. Hackers know this intuitively. (because so many of them drop out!) It's this use of artificial measurements that makes "MBA types" so despised.
If those 4 years has been spent developing real projects and interacting with real people (more like an apprenticeship than modern corporate-education) then you wouldn't need artificial measurements because people would graduate with a body of meaningful work.
And if I were an employer, it would make it much harder to determine who to interview. If you remove "dehumanizing" numbers like grades and test scores from resumes, how does Google (for example) know whether to interview you, who had a 3.8 CS GPA and a 1550 SAT, over the guy who slept through class, turned in code that didn't compile, and can't explain the difference between = and == (yes, I knew people like this as an undergrad)?
That said, this is all from the perspective of an engineering student. I suppose it's much harder to quantify performance for the liberal arts (which is probably part of what initially pushed me towards engineering, now that I think about it).