I might be off base here...but I think the Congressional Appointment part of it is more a formality these days.
The entrance process is tough. The Congress critters might have a list of people to consider, but that list is well culled by the time the final appointment is made. They have to take tests, get great grades, pass the physical stuff.
In terms of the PC part of it, I am sure there are unwritten quotas.
But in terms of toughness, I don’t think at West Point, at least,that they are less tough than they used to be. In our town we usually have one service academy slot to our high school. The last couple of kids that went were big time lacrosse players. (Our town is a BIG lax town.) They both came home after the first semester. I did not think they were cut out for it, and I want to a top 5 mil school, but not an Academy.
My daughter dated a guy from town that was at Air Force. He was more mentally tough, but still I would consider him a notch higher than your average ROTC guy from a regular college. Due to my own Mil College background, the hair on the back of my head stands up when I talk to any Academy kids. They have an arrogance drilled into them that I tend not to like. But, that is “my” thing.