It's not like running a business, it's like running a daycare. Most of these guys suffer from heavy arrested development because they've been coddled their whole lives. Think that has less to do with the wider generational stuff, which is massively overplayed in general (I went to elementary school with Antonio Brown before he moved to Miami, we really couldn't be any more different), and more to do with the fact that the entire high school to college to NFL pipeline is so heavily monetized as a trillion dollar industry. We're at the point where Signing Day is an all-day televised event (the guys who are really into recruiting are always super creepy, like making comments on the size of a 16 year old's thighs).
These players are at the center of it, and they know it. Even their social media is turned into WWE style narrative by ESPN and the other Narrative Builders. 5-star 17 year olds watch ESPN and learn from it how to act, and the colleges throw tens of millions on building them spas and marble locker rooms to attract them and then give them tutors to do their homework for them. It's all kinds of ****ed up, but it isn't something inherent to Kids of a Certain Age, it's a systemic issue with high-level athletes in the world of the internet and social media (a worse world, fwiw).
The thing about a guy like Belichick versus Coughlin is that the former is willing to bend with the times, so long as his guys play football, who cares. Guys like Coughlin try to stand athwart history and start trying to impose discipline on guys who never experienced it before.
And his coaching style is old as ****.