McRoberts didn't produce! He wasn't putting up phenomenal per-minute numbers in limited time and just didn't get an opportunity - Nicholson doubled up McRoberts' scoring numbers on much better efficiency and rebounded at a similar rate given the same playing time. He didn't get shafted by some youth movement - he was just the third best power forward on the team and they couldn't justify putting him on the court once they got Tobias Harris.
You are talking out of your ass. He was never on the team at the same time as Tobias Harris. They were traded the same day.