What's interesting about Paul Ryan's late-in-the-day flirtation with a presidential run now that it's over is what it hints at about the process. I think there are a couple of things. One is that it really was late to begin a run from scratch. It's always important not to put too much weight on "insiders told me" types of stories, but for whatever it's worth that's a large part of Robert Costa's NRO piece on Ryan's decision. My guess is that the stuff Costa heard about Ryan preferring to "frame the debate" from the outside is bunk, but that concerns about staffing up a campaign and raising money are more likely to be true -- although, again, more evidence would be needed for anything conclusive. The other is that House Budget Chair during a time of intense budget controversy is, as David Weigel said, not exactly a natural platform from which to launch a national campaign. Which is why I've never been very impressed with the Ryan-for-president rumors to begin with, and certainly not as the calendar started getting very late.
As far as the reported GOP longing for a better candidate, I'd heavily discount that. It's almost entirely a product of two things: the lack of credentialed heavyweights currently available to run, and the length and lack of visible events during the pre-primary stage of the presidential race. Neither would be solved by a new candidate jumping in. You don't get this kind of talk when you have two or more credentialed heavyweights, candidates such as Vice-President Bush and Senate Majority Leader (and former VP nominee) Bob Dole, or former VP nominee John Edwards and former First Lady Hillary Clinton. You do when such candidates are unavailable. None of it has anything to do with how the eventual nominee will do in the general election.