I disagree that "we can only be very sad" - we can be a lot of things, none of them need be sad.
Let's review comrade:
Little Mike Tyson. All 5'10" and 220# of him. Let's be realistic, he could never be a great heavyweight, right?
Christian McCaffrey. 5' 10'ish and a little over 200#. No way an Elite NFL running back, right?
Justin Jefferson. Maybe 6' and easily less than 200#. Impossible to be the best receiver in the league, right?
Becoming great is something individuals do - anyone who claims to foretell the future is foolish.
Everyone can be great. If you don't believe that, you should stay far away from children. (And I mean that.)