The fact is that its still a small percentage who are NFL prospects. So can't make rules based on that small subset. Furthermore, no one is stepping on any NFL dreams here. Players with the ability to be in the NFL have made it to the NFL just fine for decades under the old system.
Whats funny to me is it comes down to everyone being all upside down because of the massive penalty of sitting out one fricking season. Its not like you can't transfer. Go for it if you are sure thats whats best for your long term goals. One season is all it requires. And no sitting out if you have done the right thing and graduated. Yet somehow this is considered so unfair to the player.