NEW YORK — Here’s the thing about draft picks in the NBA: most of the time, they lose value once they’re used. And if you’re a team like the Knicks with 11 first rounders in the next seven years, you can’t possibly use them all. Which will eventually get us to Donovan Mitchell. For years, the Knicks stockpiled draft picks and touted their benefits in written statements. The previous team president, Steve Mills, declared that he wouldn’t “skip steps” and deplete his assets to acquire a superstar, which appealed to Knicks fans who were traumatized by the trades for Carmelo Anthony and Eddy Curry…