The same can be said for any sport with a "professional" option, so I, for one, am not persuaded by that argument. Here is a graph from the NCAA, circa 2016.
The odds haven't increased.
No one complains about rule sets for kids and youth sports progressing with age, while the opportunities for being among that tiny fraction who make a living by competing in a sport are shockingly small.
I also don't understand the argument of preparing people for careers in MMA. That's not the responsibility of the sport; wrestling doesn't bill itself as the minor leagues of mixed martial arts, so I am not certain why fans feel the need to do so.
Building a foundation for opportunities that exists beyond college makes financial sense. The pro leagues are happening elsewhere, and they absolutely can happen here, but not with American folk.