To piggyback, on this the last six seasons, Kelly has gotten good-to-great QB pretty frequently. The exceptions were the '16 debacle and '17 with Wimbush being sketchy in the passing game while dynamic on the ground.
In total, his QBs have finished with QBRs of:
12 (Kizer)
39 (Kizer)
18 (Wimbush)
12 (Book)
19 (Book)
7 (Book)
While this is his first season with top 10 QB play, he has never had QB play outside the top 20 with the exception of the season we don't talk about. It's very much overstated how Kelly can't recruit or develop QBs, but what's true is that ND hasn't had a golden arm NFL QB in his tenure, and when you go player-for-player of the ~10 QBs he has signed since he took the job only two have ultimately had ND playing careers that anyone would consider "successful". So it's the 20% hit rate that seems to drive the narrative rather than the relatively consistent production over the latter half of his tenure.
A lot of schools recruit 5-star or 4-star guys that "miss" and transfer, which is why Oklahoma spent four straight seasons taking transfer QBs. It's why Georgia took two high profile transfers this past year, and it's why a school that recruits as well as Ohio State went out and got Justin Fields. IMO, that's where Notre Dame is really handicapped... next year would be a great time to take a plug-and-play QB not knowing what you have in Buchner or Clark, but it's VERY hard for ND to take any transfers that aren't grad transfers.