Physically Brees was not that either. He got mentally better. Better at processing, reads and progressions, timing and anticipation, get the ball out quick, make the right decision, excellent mechanics and accuracy. All those were good for Brees but got even BETTER.
The best years for Brees were not 22 - 32. They really were 33 - 42 or so. Maybe some one off exceptions. I didn't look them all up. But going off memory his huge 5,000 + yards seasons with mega touchdowns were BEYOND his 30's. His processing, timing, anticipation, accuracy got BETTER as he had more experience.
Usually the biggest jump up is year 3 for a QB. So that's next year. Honestly I was surprised he was this good this soon (Purdy). No question he was better than rookie year too. No reason he can't be better yet. I think he can.