Because you're confusing two different arguments, Dayton3
There's absolutely no reason why a 24th-century military organization would act and behave like a 20th-century military organization. Because, frankly, 20th-century military organizations don't act like 16th-century military organizations. Today's United States Army has the same general purpose as, say Oliver Cromwell's New Model Army, but the standards and behaviors of the two are completely
So, yes, expecting the standards of the 20th-century American military to have relevence to the 24th-century Starfleet is a fool's game at best.
As for the second, that 26 year-olds now are going to be like 26 year-olds in the future... if anything, I'd say they'd probably be worse
in the future, simply due to greater leisure time and a higher standard of living.
Starfleet is clearly an organization that tolerates, even encourages, a certain level of individualism. (Worf's baldric, for one obvious thing. The class clowns of Corps of Engineers
for another. And let's not forget Barclay.) T'Ryssa happens to serve in an organization that lets her be
herself. And let's not ignore that Picard has grave reservations about even bringing her aboard, because
of her laxity.
You see a contradiction. I see a situation that's entirely consistent with what we've seen of Starfleet in the past, and what we know of human behavior. You're confusing the evolution of organizations with the evolution of human nature, and that's why your argument is incoherent and incorrect.