Phil downplayed the value of dominant PGs, figuring that the triangle worked in the past with journeymen who hit their spots. His successful teams relied on multiple playmakers - ie players capable of making assists or getting hockey assists.
Bulls:
Jordan, Pippen, Kukoc, Harper, Rodman, BJ, Paxson, Kerr, plus all of their centers (Longley, Bill/Purdue/Bill Wennington, etc) were tailor made for this - most of these guys were capable of averaging 3+apg given starter minutes.
Lakers:
Shaq, Kobe, Odom, Horry, Bynum, Gasol, Fisher, Walton, Farmar, Brown, Vujevic, Turiaf
So as good and versatile as Carmelo was, he had a drastic dearth of playmakers that it was almost cruel to use a system mismatched for the personnel. Rose and Lee aren't great fits - they're more about getting their own scoring opportunities. KP isn't really ideal for the triangle - he's a scorer/finisher. Noah is pretty ideal for the triangle, but he had other issues that kept him off the floor.
In any case, I think the Knicks figured out that KP isn't Paul Gasol - and he'd need a pretty big transformation to turn into a 4-5apg sort of player. To do that, it would be counterproductive to his unique capability - at 7'3" NO ONE can stop him from getting a clean look at the basket, so why should he ever pass? :)
I like what Jack brings to the table - he's a traditional floor leader who has a pretty good feel of when it's time to break plays and be opportunistic. He's a bit of an odd duck in the sense that he seemed to figure out how to play and be productive relatively late (in his prime years), and didn't establish himself as a "PG of the future" sort of player in his early-mid 20s. Thus he's bounced around a little bit as mentoring piece for young, up and coming teams and is getting starting gigs late in his career.
On one hand, you can say his body is well rested after taking off most of the prior 2 seasons. But at his relatively advanced age for an NBA player, you wonder if his knees just needed time to heal fully. I would say one thing - if he has sore knees, he's going to play through it (vs Dennis Smith Jr, whose team will hold him out conservatively) and keep the continuity going.
Let's enjoy the Jack revival while we still have it. I'd bet that next season, another would-be championship contender will pluck him away as the final piece for a championship run.