McCallum gets a bit of a bad wrap. I'm not sure there are many producers who would have stood in George's way in 1999. He was still the god of SW. Hindsight being 20/20, it's easy to say someone should have kept him in check and pushed back on some of the decisions being made. And I'm sure there are some who would have recognized the need in that moment, but in the late 90's George could do no wrong. And he had more successful production experience under his belt than McCallum did anyway. Rick was in over his head and ended up paying for it.
But the vast majority of Producers see their function as one of enabling the director's vision and only keeping them in check from a monetary perspective when they reach too far. Money was no object on the PT, so he ended up just doing the enabling portion of the equation. I mean, even Spielberg was afraid to check George too much when he was asked for input. If Spielberg didn't have that weight in that time, who would?