Typically those undrafted guys are missing an element to their game. Back in the days, most college players were either undersized or too slow. Even Hobey Baker winners like McPhee had issues making the league.
Better players are going to college now, but if you take a deeper dive into those 37 players you'll find some sort of deficiency and a reason why they didn't get drafted. You're arguments are entirely based on stat watching, if that's all it took then Riley Barber would be a full time NHLer, he's been at the top of AHL scoring the past few years.