This is demonstrably untrue. College football does not have better players than XFL and college basketball does not have better players than the development league. Yet, both the college football and college basketball revenue and television market are huge, while they are non existent for the professional leagues with better players. Your post implies that there is no brand or goodwill associated with either college sports or with the universities themselves. This is an absurd statement. It would be equivalent to saying you could open your hamburger restaurant with better employees / ingredients and will make more money than the local McDonald's.
Also, you cannot use straw man arguments to demonstrate the flaw of someone else's point since, by definition, you are not arguing against the other person's point, but rather straw man version that you created in your own head.
The existence of competitor leagues that haven't outdone CFB does not disprove the existence of a player market inside the league.
Obviously there's a lot of name value in the university programs but that name value won't be maintained for free if they no longer compete in the market for talented players. Look at... well, look at Georgia Tech. Yes, it takes decades to piss away name value; no, that doesn't disprove the existence of a market.
Here's the thing: you're claiming that there isn't a market *despite the existence of market participants spending money in that very market outside of just the top few programs.* The evidence of there being a market is crystal clear, it's that there are participants in that market. And as you point out, the market for college basketball players is actually a *hotter* market than the G-League one. It's not an *independent* market - it exists because of existing brand value in the programs - but it's there.
You seem to be doing two things:
The first is ignoring path-dependency, claiming that because you couldn't immediately replace college sports by hiring away all the best players that there is no value to the players. *Where* the market value is depends on the path; *what* the value is, much less so. The claim here is about the latter. There is value to having the best players within the college structure, even if the value of having the best players outside of the name value isn't enough to overturn a century-old institution overnight. It would take magically erasing a century of history and starting from scratch, *but nobody in this thread is arguing that that's what the players should or could do* - bit of a, what's the word, strawman.
The second is substituting collusive ideas with any idea of demonstrating if a market exists. You pitched the scenario swapping all the current players out and sub in new ones, and then have more success than the former players trying to set up a new league. What is this supposed to show beyond that players in a some markets can collude to reduce the competitive cost of the market? What *actually* happens makes the opposite point - the players in the market, *without* a strong collective organization reigning in their behavior, are aggressively competing for players in college sports, even that the middle levels.