I have seen essentially this sentiment several times on here, and haven't chipped in my $0.02 ... until now
I entirely disagree with this statement. Not because "5" rated courses shouldn't be amazing, or the very upper tier of courses, but because they shouldn't be "perfect" or "almost impossible to create" or something similar.
I agree that the absolute top end of "5" should be "perfect" or "almost impossible to create", but part of the problem of having a rating system of 1-5 is that each of these numbers encompasses a range of courses. There should be courses that are a "bad 5" as well as a "good 5". Having all of the courses in the world, save 2 or 3, fit into 1-4, and then having 5 reserved for just a couple is silly, even if you view the scale as more of a "bell curve" than straight line.
As I say, just my $0.02, and I haven't rated anything 5, though my rating of Flip/Leviathan/Beauty/Beast is still pending
BLM