Shaw was able to extend the lifespan of the Stanford offensive success after Harbaugh left. Even in his last year, he had good QB play from McKee.
But he wasn't able to maintain the success in the trenches that they had under Harbaugh. Luck got the headlines, but Stanford was winning both sides of the trenches against nearly everybody. Those front 7's with the likes of Shayne Skov, Trent Murphy, Ben Gardner, Chase Thomas and Jarek Lancaster were absolutely dominant. Then time went on, those guys left and they weren't replacing them with similar talents. Their fronts were getting smaller and smaller and less imposing. Sure, they got a few more good years out of it, like in 2015, '16 and 2017, but those were carried primarily by the offense and notably the elite play of Christian McCaffrey and Bryce Love.
It has come to a head in the last few years, where their OL and DL play has been flat out putrid. Which makes me wonder why Michigan went after half their starters on the OL when they were quite bad.