Remember that once a player is signed, they don't have to remain with the team.
Signing kanter would be about keeping a very young, talented, ASSET. The jazz could trade kanter, favors, Burks, trey, Hayward, gobert, in some combination for a proven all star. Possibly. (Think Houston, okc, harden)
Yeah, but it only takes 1 team to offer Kanter a bloated contract that no one else besides that one team wants. Also the reason for not signing may be financial. If he cost 15 million, we have to take nearly 15 million back in a trade.