You raise some good points but, the problems are:
Admissions aren't controlled by the Corps, they're controlled by the University which means it is subject to the current - Top 10% admissions problem. Several of my buddies who have done very well wouldn't even get in to the University today. This includes one guy who is an O-6, another guy who is a prominent public figure in Austin and another guy who is responsible for recruiting a substantial number of cadets into the Band.
The Corps is there to develop leaders and many of those will go on to become officers in the Armed Forces. The cold harsh reality of getting your choice of what you want to do in the Military is that you need good grades. While we all know that a degree from A&M is solid, those who do accessions don't necessarily distinguish between a degree from Texas A&M and a degree from Delta State University.
When we were looking at colleges two years ago, Virginia Tech was one of the schools we visited. They touted their statistics for Army cadets getting their first choice of branch and Air Force and Navy cadets getting pilot slots - including drones for USAF. They said the key to their success was bringing back former cadets who got pilot slots to tell the current cadets that the key to getting a pilot slot was good grades. They said that cadets don't listen to the staff/cadre but, they would listen to current junior officers in pilot slots.
My point here is that the "customers" for these "leaders" want to procure students with good grades. So, fortunately or unfortunately, in the Corps mission of developing leaders, helping students make good grades becomes really important.
Remember, students who want more out of the Corps can always do Rudder's Rangers, Ranger Challenge, Seal Platoon, Ultimate Frisbee Club, FDT, PMC, etc. Oh... and of course, I almost forgot - Aggie Band.
Back in the 1980s, I became a firm believer that the Corps could take anybody off the street and make a leader out of 50% of them. However...things are different today. We don't have 2 million military on Active Duty and there is no West Germany. So... the current military situation determines a lot of what our Corps needs to do. And since we don't have the Wild West admissions policy anymore, a set of strict requirements determines who we get to intake as cadets.