Looking at the classes Harbaugh has had with kids that were ranked 4/5 star:
2015: six 4* - one played in the NFL, which is the same amount of kids that became sexual predators from this class (Grant Perry)
2016: one 5*, 13 4* - 5* starts in the NFL, two 4* have made an impact in the NFL (Devin Asiasi transferred to UCLA though, so he doesn't really count)
2017: two 5*, 18 4* - one 5* was a late round pick already a backup on his 2nd team, other one has done nothing; one 4* transferred to Minnesota and starts in the NFL, one 4* is being elevated by Stroud after a few years of not much at WR, one 4* was a 1st round pick but isn't good, and one 4* is a backup after a very ugly transfer situation that made Harbaugh look awful
2018: one 5*, five 4* - 5* has done nothing, one 4* is an elite young player in the NFL, one 4* had a brief career and has done nothing after being awful
2019: one 5*, 14 4* - 5* is solid young NFL player, one 4* is solid young rookie but transferred to UCLA so he doesn't count, one is an underwhelming 1st round rookie DT, one was a 2nd rounder who has made minimal impact
2020: 15 4* - none in the pros, though a 3* might be a 1st rounder at guard
That isn't a good hit rate, and 21 of those kids were top 100 recruits. I think the biggest issue Harbaugh deals with is his complete inability to develop the skill positions. He hasn't had a RB, QB, WR, or TE that played their entire college career under him actually end up doing anything after michigan outside of maybe DPJ, though it was brief and now he's fighting for a backup spot in Detroit. He probably should've gone to OSU afterall.