Saying Rees is hamstrung by Kelly is patently absurd because it assumes Rees knows enough about offensive football to be hamstrung by any head football coach. Rees can't challenge/change Kelly's offense system because it is really the only offensive system he knows. His overall lack of experience is appalling for an OC position at a Power 5 conference.
Rees' lack of experience is a major major limiting factor for ND. I think you would be hard pressed to find a less experienced OC in all of Power 5. One year as a trainee and one year in an entry level coaching position outside of the Kelly system is hardly experience worth noting. Kelly picked the low hanging fruit and we are stuck with the same old crap Kelly offense because what Rees knows about offense compared to his peers could be put in a thimble.
In the 1st Clemson game he got lucky as Clemson was down half-a-dozen defensive starters and then he got absolutely schooled by Brent Venables in the 2nd Clemson game. It was far more than Clemson just having good players on defense. Rees' couldn't adjust the offense because he doesn't have the experience to adjust the offense. Look, we didn't lose the game because Rees was the OC but the next game we win because Rees puts in an innovative offensive game plan won't any time soon.
Compare his experience, as one example, to Charlie Weis Jr. who is actually one year younger the Rees but has far better experience. CW Jr. is said to be the youngest OC in D1 but he is only at Florida Atlantic. Just being around his dad, (whatever one thinks of him he has excellent offensive experience) easily matches whatever Rees learned playing qb. He also worked under Saban, Lane Kiffin, Steve Sarkisian and now he works for Jeff Scott who was OC at Clemson. I'd take CW Jr. in an instant as OC over Rees but we know Kelly isn't going to hire outside his comfort zone unless he has to.
I'm sure Rees has the makings of being an excellent coach someday but he is far underqualified to be the OC at ND and is way too far out over his skies. ND will pay the price in more than just the Clemson game. Blaming poor offensive performance on the talent is incredibly simplistic. The next innovative move Rees makes will be his first. Rees would have been far better served if he left ND and really coached for 3-5 years under someone who has more diverse offensive experience than Brian Kelly before becoming an OC somewhere. Rees will show his stripes next year when he doesn't have a 2.5 year starter in his 5th year playing for him.