Is Coppy the only person on the planet who's ever questioned defensive metrics?
Or is he just the one mentioned when you want to make that point?
The same people that question defensive metrics are the same ones that questioned OBP 17 years ago.
The tools to measure defensive contribution have greatly advanced in recent time. It wasn't outlandish to question the science in its form prior to have the ability to chart movement.
The is a difference between being skeptic on it's exact value and outright denying it like some have.
I understand that it can be hard for some people to wrap their minds around an all around above average player providing more value than a traditional 30+ homer slugger who is a one dimensional player. For so long that has not been the case in popular opinion as well as the free agent/trade market. Thankfully that has changed.
I thought questioning them at all was only an act of dinosaurs - didn't you infer that two posts above?
I don't think anyone - Coppy included - questions that there's absolutely some benefit to be gained from them. It's just as you mention - weighting them accurately is the important part IMO.