I'll just interrupt the lovefest to remind you that in the NBA, your position is the one you can defend. The incredible evolution of team defenses has muddled the issue somewhat (and we all know about the few notable exceptions like Draymond), but IMO the rule still applies pretty well to starters in particular. Collins cannot defend the 5 spot, so ideally he's more like a bench center used for spot duty or a starting 4 who wants to hang our near the basket (which is not ideal in the modern NBA where the "PF" should be a floor spreader above all else).
I mean the whole league considers Collins a tweener and his time in Utah hasn't changed that. If we want to play him in the middle, it immediately creates a defensive problem. Kessler is the only guy on the regular rotation who can really improve the rim protection / low post D of the Collins lineups, and those two are very incompatible on the other side of the ball because Walker parking himself and his defender near the basket prevents John from doing the things he does best (diving/flying in from the weak side for oops and offensive rebounds).
In short, Collins is a bit of a luxury to begin with, and his contract exacerbates the situation. This is basically why Atlanta traded him, and the exact same factors are in play here. John has played well lately, but his role has largely been that of a pogo stick garbage man who crashes the offensive boards hard and gets an alley now and then when the D forgets him. And paying a garbage man over $25 million is just stupid. But hey, it's not my money, and I wouldn't trade Collins now as the offense is really humming.
As an aside – I hope people realize how much it hurts us that Walker is so ridiculously one-dimensional and lacks all ball skills. He's part of the Collins problem as he prevents us from using many player combinations that would otherwise work. Moving Kessler to the bench has been one of Hardy's best decisions ever.