You need to keep throwing it against the wall with your best estimate of the top QB's that are a reasonable fit and hope some stick. They fail so often at both levels that you can't just get one you think will be the answer and think you are done. Until they have proven it, you keep loading up. In the pro's it's a little easier as you can keep that QB once you find him for next to forever if you are willing to pay. In college you need to keep trying to get the best every year because even if you find 'that guy' he'll be gone in a few years.
And yes, it sucks, but it's also going to cause havoc because you'll get more transfers out if you are doing it right, but that's the model for having a consistent contender. No complaints about Book. He was a 3 star that has well outperformed his rating, and is one of the best college QB's in the last few years. He's helped get ND where they are now and he and Kelly should get credit for his development. But....although he's one of the better QB's in the last few years, he's not a Lawrence, Fields, Burrow, Murray level talent.
Maybe Buchner will be the start of a consistent progression of top level QB's. I hope so, but they can't stop and think they have answered the question with him. Sometimes guys don't develop. Sometimes they get hurt. Sometimes they transfer out or get suspended. Regardless, they have to keep pushing for top level QB's every year.
Regarding the O, we do great at recruiting all but the flashy skill positions. We've consistently have top level talent on the OL and TE. WR's is a little more hit or miss. We gotten or developed some top talent, but just not a group all at the same time. Recent recruiting indicates we may have turned a corner on this, but again, you have to keep after it each year. RB is weird. Kyren wasn't an all world recruit, but I'm more than happy with him and Tyree was a big time get, but given the OL and TE's and our success with lower rating RB's you'd think that the top RB's would be banging down our doors to get in. But it seems even when we get a good one, it's a harder sell than it should be and we don't have that pipeline of talent that the elite teams seem to get.