The Irish were chasing a regular season championship late in the season. On the flip side in terms of standings, the double bye in the conference tournament wasn't a lock until the final game.
Most of the conference wins were close games, not decided until the final minutes. If playing guys who aren't quite ready costs points, some of those wins could easily become losses; so when you wish they got more reps during ACC play, were you willing to risk the double bye to get those reps? Were you willing to give up early on chasing a first place finish to get them those reps?
There were a couple of blowout wins - BC and Syracuse. Maybe Mooney and Burns should have played more in those games, but I'm not sure that mop-up time is particularly meaningful.