I think Ursa is probably right that most MBB fans don't care about the stars and the future nba talent. The impact to MBB ratings if you ended OAD would be negligible. If, for the sake of argument, the top 100 HS players never went to college and went into some kind of "super G league" or even directly the NBA, I suspect the NCAA ratings wouldn't miss a beat. And nor would be the NBA's ratings change either. And let's face it: even if the G-league had these stars that used to play in MBB, nobody still would watch that either. Even a developmental league with DeAndre Ayton, Mo Bamba, Marvin Bagley and Trae Young would do nothing to make people watch it.
The NCAA may be a "corrupt" organization but it has a great product and the value of that product isn't dictated by the quality of the talent. Even without those top 100 players in the theoretical argument, it would get by just fine. The value of MBB, and more specifically the NCAA tournament, is driven by the schools themselves, the uniforms, the fame of the coaches involved, the underdogs, the rivalries, the upsets, the bands, the mascots, the gambling potential and the drama of it all. Losing OAD talent (or more) would do nothing to lessen that value.
While you may lose a small number of the hardcore basketball fan that misses these stars and would opt to watch the NBA/D-League, you probably win back some the fans who have tuned out because so they find it harder these days to connect with and root for teams (like Duke) who replenish the roster every year with more 1-year talent.