The portal is nothing more than the NFL model being pushed onto college football. Players have no loyalty to teams or schools anymore. Their only loyalty is to NIL money and self promotion.
That's partly correct, but this is worse than the NFL model. The pros would never even consider a model where there is 0 obligation on the player's part. The NFLPA would never even ask for such an absurd thing. Players coming and going as they please.
But your last sentence hits on why this is the death of college football as we know it. Like the portal or not. Like NIL or not. Truth is, the quintessential element of college football WAS the player/fan bond. You saw a kid come in as an 18/19 year old and, in most cases, saw them leave as 21/22 year olds. A handful would go pro early (which meant they probably did very well for your program) A few others would transfer out, but in the vast majority of cases, that was indication that they were never going to get playing time and they wanted to go somewhere they could play.
That fan/player bond was one of the, if not THE, key distinguishing characteristics of the sport that set it apart from the pros. Except in rare cases where you had a Paterno/Bowden/Saban type coach, fans mostly identified with the players. Coaches could come and go, but, by and large, players were locked in on the program. You loved your guys and hated the other team's guys. Now, a player you were cheering your heart out for one year could be the opposition the next season. Knowing that reality erodes the fan/player bond, which destroys the fabric of the game. Just the reality of it.