I wouldn't disagree with you the zone last year was a half-assed changeup to mess with the other team occasionally and/or an attempt to keep Osunniyi or King out of foul trouble.
They weren't committed to it from a scheme perspective, never seemed to have their heart into it the way they did playing man-to-man, and their personnel wasn't a great fit for it.
One of the intractable weaknesses of a zone defense is it allows your opponent to dictate matchups. You have the same problem with the "switch everything" man-to-man style against the P&R.
The point of having a guy like Kalscheur on the roster -- a good though streaker shooter but a beast of a man-to-man defender -- is to erase your opponents' best perimeter scorer or at least force them into a degree of mistakes and inefficiency that means they're dragging their team down with them.
Football schemes run into the same problem. Unless you're playing some sort of man or matchup concept with coverage over the top from the safeties, then that lockdown CB might not always be matched up with the best WR on the other team. And you know the offensive coordinator on the other side is doing everything they can to get their best players away from your best CB. Dictating matchups is power.
Putting a guy with Kalscheur-level lateral quickness but small size/wingspan for his position is just a waste of resources in a zone. There's a bunch of reasons it was never a primary look the past two years.
I agree with you this year might be different, though. The athleticism and length is there to do it. There isn't an ace defender (though Gilbert could emerge as one... Lipsey is close) who you want dogging the best player on the other team any time they're on the court. A zone might actually be useful for hiding Milan.
I'm sure we'll see more and a better version of it this year.
I just think a defense that lets an opponent get their best scorers away from a guy like Kalscheur without too much trouble is a defense that isn't maximizing your strengths as a roster.
