The title "Scrubs: Med School" is fine for me as a spinoff. Different performance of the intro song, fine. We've got a new POV character, a new gang as it were, younger, even younger than the original crew, they're not first day interns, they're med school students, so they're even more raw and incomplete as people, they've got earlier lessons to learn.

They didn't give the first series time to rest, they had no faith in the new concept or the new cast, so they bring back a lot of the old cast to...exist? They had all gotten one of TV's biggest "and they lived happily ever after"'s, so they're not really able to have growth moments and drama of their own, they mostly serve as rocks for the new cast to bash themselves against.

If they'd given it a few years to let the audience start wanting more, and then focused entirely on the new crew with maybe one of the original actors in a recurring role (like have Cox or Turk as the hospital administrator, Kelso's role) and maybe have other characters return as single episode guest stars the way Michael J. Fox and Dick Van Dyke did, and you know, have any faith in the concept at all, it would have gone 4 seasons.