Only because people like to crucify him based on previous years' performances.
What people tend to overlook: 1) he played under Casey 2) teams loaded up on him because Ibaka/Val/CJ Miles/OG were not offensive threats, hence the spacing was garbage
When Nick took over he improved Ibaka's game and said "yea take those mid-range jumpers" and even ran those pick and rolls so he can shoot them.
IF you were to insert him on this team there are way more reliable shooters now than there were before. Part of this is the improved development and experience players have gained (VV, Powell, Siakam).
If he was on this team he is another player that could command double-teams. Additionally, you could get him to work the post on smaller defenders and draw double-teams which the raptors could punish by having shooters (VV, OG, Gasol, Lowry, Siakam) out there with him.
In the East, the shooting guards he would post-up on: J. Richardson/Thybulle/Korkmaz (sixers), Jaylen Brown/Hayward/Tatum (celts), Wesley Matthews (bucks), Jimmy Butter/Tyler Herro (heat), Oladipo/Brogdan (Pacers).
we only have 1 1-on-1 post player: Siakam.
And yes his defense is something people like to bring up, but the question that should be asked is whether his offensive presence does more than compensate for those shortcomings.
However, if the Raptors were willing to trade for him it would cost Ibaka or Gasol, which IMO is too much, unless there is a second trade to replace Ibaka.