They were starting to decline even before Mitts. The competition level jumped up in a big way for the last decade. Several also rans in Minnesota, like Mankato, Bemijdi and a few other schools built up their programs. More high end guys started going chl routes or other schools that in previous generations would have been locks to ve Gophers.
They haven't had a truly high end kid since Wheeler, Vanek, Kessel, Johnson hay days of the mid aughts.
Granted Mitts was a top ten pick, but he wasn't a great ncaa player and didn't have a lot of good players around him on that team.
They will bounce back with the right recruiter.