I agree with the OP, Paul Pierce didn't really change.
Realize, Shaq gave him his moniker back in 2001. Yes, Shaq saw the truth!
In essence, it's like dumping a John Havlicek, but instead of on the Cousy-Russell Celts, the LA Clippers. He would never have had the "steal heard around the world" or any of those famous mid-70s duels with the Knicks, Bucks, and Bullets. This is why Hondo became a hero so early in his career; the same goes for Bird, since Red had to wait a bit for his arrival during the late 70s drought with the first Gaston, I mean Brown, as the owner.
If you look at a younger Pierce, and put him in the exact spot as Bird, circa 1979, with Fitch as a coach, Maxwell, Robey, Tiny, Henderson, and retiring Cowens as peers, we would have gone just as far in the playoffs before the arrival of Parish and McHale.