I loathe to defend MLB for ... well, anything, but the scope of the minor-league stadiums left them in a no-win situation. They *had* to come up with some way to get the oldest parks up to the current standards.
Our local stadium was like 15 years old when that came out, and in amazing shape and condition, with great amenities, and there was a lot of hand-wringing when they had to find room and money to add locker rooms for potential female umpires, and food-service areas and workout space for the visiting teams, LED lights, etc.
I can't imagine what some of these oldest parks would have had to do to become "compliant," but the threat of losing the team seems to be the only threat that carried any weight in a lot of these places.