Allow me to try to simplify the sabermetric revolution as much as I can:
Late 20th Century: we are evaluating baseball players
Early 21st Century: we were so wrong about our baseball player evaluation!
Less Early 21st Century: we were so wrong about our baseball player evaluation, again!
First, there were players, then there were numbers. Then there were better numbers, then there were still better numbers. The numbers will only continue to improve with time, and a lot of the things we currently think we know about baseball will probably end up being at least partially untrue. Keep that in mind next time you express a particularly strong opinion. But anyway.
Several years ago, people started to care an awful lot about on-base percentage and offensive productivity. This was warranted, because it is important to get on base and be offensively productive. A little later on, people started to care an awful lot about defense. Turns out some of those OBP-happy sluggers were subtracting runs almost as fast as they were adding them. Whoopsadoodle.