Information can be communicated in a movie through means other than dialogue. You can try to retcon the information you're given, sure, but that doesn't mean the information isn't there.
The clones in Episode II & III are uniform height, weight, have the same face and the same voice. You see them doing almost every possible job there is EXCEPT for filling Officer roles or Jedi roles, so that means pilots? Clones. Gunners? Clones. Troopers? Clones. Technicians? Clones. The visual information is there in the prequels. Either you're a Jedi, you're an officer, or you're a Clone. That's your republic army.
Then the republic becomes the Empire.
Look at the Empire in the original trilogy. The stormtroopers have different heights, different voices - and Lucas made sure to NOT overdub all the trooper dialog with Temuera Morrison, the way he did Boba Fett. He easily could have. It would have taken Morrison what, another 3 minutes? But that decision wasn't made. There's a reason for that. Plus, keep in mind that the Academy Luke wants to join is an IMPERIAL academy. What do you think they're training for? Those people are in that academy to become pilots and troopers and hopefully even officers. If Stormtroopers, TIE pilots, gunners, technicians etc. are all Clones, then why are you opening academies and having people train for those positions?
You're wrong.