It was a mess because WOTC was caster biased and kept spewing out new spells and new ways to cast spells. Then abandoned them.They did that in 3.x and we had dozens of classes. It was a complete and total mess for no reason. I like the flexibility we have with 5E and think the subclass system works well. You play a couple of games, figure out what kind of subclass is going to work best for you and the group.
The problem was never the amount of classes.