SP+ does a much better job of providing an objective rating between eras of past, current, and future team performance that mere W-L on their own. W-L are what a team accomplishes, though, you are correct about that.
SP+ also adjusts for strength of schedule and the strength of those victories. If W-L was literally your only goal, then we should be scheduling three cupcakes in the non-con every year (including dropping good 1-AA and G5 programs like UNI and Louisiana from future schedules, only the dregs here, no more Iowa). I could even take that further that, if the only thing you want is wins, then we might as well drop to the MAC instead of playing Big 12 opponents.
You would say leaving the Big 12 to win games is absurd, and you are right, but that is an implicit admission on your part that not all wins are exactly created equal. Beating Texas takes a bit more than Bowling Green State.
I repeat -- if you think things now are no better than the Rhoads era, then you have your eyes closed. Bring those early Rhoads teams into our modern schedules, and they are not going 3/4 on bowl trips. And the late era Rhoads teams, well, wow, you see what happens when Rhoads had to play a full round-robin against the B12.
I understand all that. My point is simply that wins matter as well and I don't like systems that simply disregard that. We've had this discussion on the basketball side with KenPom and others - there is value there but W/L must be taken in to account.
Furthermore, I actually do think we should just play the dregs for noncon and drop Iowa. Wins matter more in football than other sports because those wins directly lead to better bowl bids. IMO best way forward is to stay in the Big 12, but also to maximize wins. Your noncon schedule is the only thing you control there. I know others disagree and that's fine.
Also it's dead obvious that Campbell is better than Rhoads, for no other reason than this team just doesn't get blown out that often. The game on Saturday, ND, that's basically twice in 3 years. That means something, especially that I just look forward to every game. I mean to take nothing away from Campbell. I hope he coaches here literally until I die. But winning games matters.