I think comping an incoming freshman to one of the top-10 players on the planet does a tremendous disservice to the freshman. At the age K2 is now, Luka had been playing against men for 2 years with Real Madrid, not boys in Wisconsin, so no a 19-YO Luka would not have been precluded.
If you want to ignore that K2 faced the weakest competition of any player on Duke's roster and has athleticism concerns when evaluating him, knock yourself out. TJ was not as skilled as K2 but he was skilled and more athletic than K2. TJ couldn't see the floor with Mark Mitchell in front of him. K2 has Cooper, Sion, Mason, Caleb, and Evans looking for the same minutes.
I do think K2 will be a great player for Duke, I would just be surprised if it is this season.