Nash is quicker because HE TRAINS. If you don't workout, sprint training, play soccer like Nash does in the offseason... you will will love muscle memory much quicker as you get older. INACTIVITY is the quickest way to lose athleticism. People like Kobe and Nash are always active its the reason why they lose their athleticism at a snails pace.
That's fine, but that's besides the point. The point is, when AI lost athleticism, he lost his game. Guys like Nash and especially Kidd, were a lot more athletic in their 20's, but when they lost it they still had skills to make other players better.

When Kidd brought his old ass to the Knicks this year, he had a visible impact and made things better. I don't care how much AI keeps himself in shape, he won't be blowing past people like he did when he was in his 20's or even early 30's, that level was insane. He also isn't the type of player that makes others better, he was a one on one specialist.