Would CMP have done better with Archie's roster last year? Unequivocally, yes. With your assumption, you allude to Archie not being able to modify or change his system based on his personnel. CMP has shown that he will change his tactics and coaching based on who is on the roster. I also think a lot of other coaches could have made IU a tourney team last year....last four in likely, but still a tourney team.
I would argue that Archie didn't WANT to modify his system to fit last year's team, and I applaud him for it. Not that he couldn't. He took over for Tom Crean's players, who were accustomed to playing a certain style. Now he could have played a style more similar to that and probably done it better than Crean did, and had a slightly better season. But that's not what he wanted to do in his first season as head coach. Why allow the players to dictate how the team plays if he knows it's not what he wants to do in the long run? In his first season, he wanted to set the tone, build a foundation, teach the team to play tough nosed, gritty basketball. He commented before last season that he spent 75% of practice time on defense, and didn't focus much on the offense. I'm sure he knew, or at least assumed that the team wouldn't be great last year. But he used that season to build an identity and teach the guys how he wants to play, breaking old habits. Now this season he starts to bring in his own recruits and groom them to play the same way. Now he has a foundation of returnees who have already learned for a year how to play the way he wants. He wants to play a style of defense that thrives with players that have length and athleticism. He didn't have much of that last year. You'll notice with his first recruiting class, that he brought in a lot of length. He could have played differently last season to fit his current players better, but he knew that wasn't going to be his long term approach and those players won't be there forever. He rather chose to start teaching them his style right off the bat. I think it was a good decision and will pay dividends this season.