The one thing that that I will say about the CU's running backs, is that in the end the best guys always seem to play. That is probably the most important thing about the position. Clayton could be an exception, but who has been a CU rb that transferred and really did anything? Darrell Scott-- 2 games for UCF (He got beat out by Speedy Stewart). Marcus Houston, I suppose he was okay at CSU (the knee injury took quite a toll), but he was beat out by 2 guys that went to the NFL . . . Chris Brown put up a pro-bowl season or two. PT Gates, don't get me started. Michael Atkins, injury then got beat out.
I think you would have a point, if there was an exodus of P65 RB's from CU that went on to do great things. The only guy I can think of was the RB from Wisconsin (Brian Calhoun? another top-10 RB recruit that played as a Frosh/Soph?, and decided to move home). For RB's at CU, I see more of the flip-side-- Phillip Lindsay progresses such that he makes an NFL team and is a pro-bowler. Broussard comes from nowhere and is PAC-12 offensive player of the year. IMO, they are generally finding and playing the best guy. For Hagan & KD, I think it was a big gamble that they went with Broussard out of no-where, but it worked out.
There is reasonable frustration about finding, promoting, and playing the #2 back. That is always a tough go, unless you blow out teams or you are being blown out. From a coaches perspective, when the game is contested, I imagine it is tough to hand the rock over to a young RB with the fear of a key-fumble or completely missed protection. That is a complete landmine and CU has been conservative in that regard. Would we have liked more carries for AC, absolutely but if it cost CU a game during crunch-time? Then there is a ton of egg on the coaches faces. Also, the player can get even further in the dog house or not develop--a freshman fumbles in crunch time, the teams loses, and then the player blames himself--look out. All players develop on their own and their coaches time-frame. IMO, RB's usually take a couple of years. Houston played great as a Freshman until the injury, but he was the #1 RB in the class.
I coached competitive hockey for almost two decades. You face a similar conundrum with centers and face-offs. Our teams had tons of great young players, some of whom had mad skills, more speed, better stick skills, and a ton more flash at the center position; however if you are nursing a 1-2 goal lead in the 3rd period, the center that plays is generally the one who can: (a) either win the face off, or not lose it clean; (b) can tie up whoever needs to be tied up, usually the opposing center; and (c) instinctively knows the post-face off positioning (however the face off turns out) by wrote. Although you would love the extra insurance goal, the name of the game at that juncture is keeping the puck out of your net. I think it is the same thing with young RB's and carries during a contested game. It is just something that takes time with responsibility, patience, trust, and seasoning from all involved.
Also, one last thing-- CU was playing a new QB. I'm not sure if CU would have fallen behind with a turnover at some key juncture in the 2nd half, they could have played very well from behind. Again, more experience, talent, or comfort at the QB position, maybe the coaching staff would have rolled the dice more frequently.