I think McDonagh's success is about the Rangers getting back to a speed game too. When he's using his instincts more, he's a better player. When the Rangers play with speed, McDonagh has to rely more on his instincts.
The reason the team looks so different than last year is because they have speed and depth again. The reason they look so different than they did in the President's Trophy season is because they generally are having to actually put in the work to score. In 2014-15, they seemed to be able to score almost at will on the rush. While that's all well and good, it meant there was never a structure to build on in a game where they took the lead. They could protect that lead successfully, but always on their heels. When you're already putting in the work to get zone time and sustain a forecheck, it's easier to keep that going even when you're ahead.