That is a fallacy. Shaq's prime spanned from 94 to 03, peaking in 2000, he simply got better teammates and coaching after 99.
I would say his passing got better after 95, 96, but he has always been a tough matchup.
His game has always been overrated some bit, yes he was dominant, and yes he was one of the toughest matchup in the history of the league, but he rarely gives 100% (see his playoffs), is only about average on defense, and was never as dominant a rebounder and scorer as he should / could be. How can a man of his agility, size and atheleticism only lead the league in scoring once, shot blocking zero times and rebounding zero times?