Brees could still sling it downfield and drop it on a dime. His anticipation on downfield throws was still legendary. But the velocity just wasn't there anymore.
I mean, lots of his deep balls were coming up short in the last couple years. He always compensated for his lack of a big arm with anticipation and accuracy, but at some point the velocity was bad enough that even great anticipation and accuracy weren't enough when trying to hit a moving target.
But, I'm sure he could have hit a dime at 60 yards as long as it didn't move. :)
Anyway, he could still do it on occasion, but he wasn't as consistently amazing at it as when he was in his prime. Which is why they kind of took out a lot of the "shot plays" that they ran when he was younger.