The NBA is unreal. Obviously, I'm a big Iowa fan, but I also watch every Nuggets game.
If you don't follow closely, you can't even imagine the depth in the NBA. The word "elite" barely scratches the surface.
NBA teams carry 15 players. It varies from team to team, but you can make it simple and say it pretty much breaks into thirds:
1-5: Starters
6-10: Backups
11-15: Practice squad
Your "practice squad" is really only going to get on the court in garbage time or in extreme "situational" scenarios (hands team, length team, etc).
The Nuggets have the 2020 Pac-10 Freshman of the Year (Zeke Nnaji) as a "practice squad" player. He's played well in garbage time and shows signs that he may be working his way up in the rotation, but the point still stands - when you have, every single draft class, talent like that flowing into the game, it makes things very tough. Teams would rather put resources (travel expenses, coaching time, contract money, etc) into a 20 year old like Zeke Nnaji is going to turn into a rotation guy in a couple years rather than spend a roster spot on a known quantity like Uthoff who, at least per NBA scouts (apparently), is unlikely to develop into a rotation quality player.
I'm sure it's very hard to swallow and I feel for the guy - I loved watching him play at Iowa - but the reality is Uthoff is probably plenty good enough to make all sorts of team's "practice squad" but, from the perspective of those "in the know", his upside is well-understood to be below "rotation quality".