It's an easy thing to say, but...
It's not necessarily true. It's a bit like saying free agency ended the dynasties in pro sports, which at first glance makes sense. If you could just keep a Bill Russell or a Babe Ruth, having a dynasty was much easier. But we still saw dynasties form after that.
Kiffin's statements are under the assumption that rosters will still have to radically change from year to year, but that's not necessarily the case. We're seeing the rise of extended eligibility, I predicted that with NIL and Alabama is about to face a guy playing in his six year of college football.
How does that apply to potential dynasties? Well, let's say Oregon football ends up with a pretty good trio of skill players. Let's say for example, it's along the lines of Jacob Coker, Ardarius Stewart, and Derrick Henry.
I chose Stewart (instead of Ridley) and the year Coker was there for a reason. Coker and Stewart both made less than a million a year under their rookie contract. With current NIL payments, paying them more than that, especially for a program like Oregon is trivial. Even Henry was making less than two million a year!
So, you offer Stewart and Coker a million a year to keep playing college, and you expect continued development from both of them. You pay Henry 3 million a year or so, and he continues to brutalize college football. You can build a dynasty around that sort of thing. To apply that even within current confines, Cam Newton only played 3 years in the FBS and one of those years he played little enough to redshirt. So, you can have Cam Newton at least two more years without changing the status quo.
That's just one scenario, but NIL, rich boosters, and breaking the eligibility rules will open new pathways to domination. What might be more accurate is that we can't necessarily expect the same dynasties we've seen in the past moving forward, because now it's more about deep pockets than anything else.