Bjelica doesn’t move or look like an NBA player. I’m glad Kerr has such a short leash with young players cause Kuminga is capable of making a difference with his athleticism.
Even though Wiseman may just be mediocre when healthy it will still hurt not have that body against Jokic, Gobert and Ayton.
Bjelica has some chronic back injury. When they signed him he looked really good, spaces the floor good passer etc but then he got hurt and now it's become apparent why he was available. I don't know exactly what it is but he's had a series of minor injuries that are apparently all connected to the back. So he moves really stiff and upright and it's because of the back. He was a big reason not getting Wiseman back this year was a blow Bjelica is playing so poorly that they really needed a new big as you said.
Kuminga has been playing more I think recently he hit a bit of a wall and his defense has been problematic teams are attacking him more. So my guess is Kerr was afraid Phoenix would exploit him.
I can see next year if Wiseman is healthy, Kuminga more experienced, poole a year older etc the young group could really be good the problem is Steph and Klay and Draymond will all be a year older.