just dump Charizard, Squirtle, and Bulbasaur at Oak's, then you have a bunch of pissed off nostalgiaphobes, the kids still hooked on Kanto which was all Pokemon had at the time, whining about how poor Charizard, Squirtle and Bulbasaur got cheated out of screentime and proper battles. And I guess the writers figured that having this "nobody" team be stronger than the originals would have been a giant slap to the face of the fans, so they made them as weak as possible.
This is what I probably figure, the writers purposely sabotaged Ash's Johto team on purpose because they knew how popular his Kanto Pokemon were. They knew they had to replace them for advertising purposes, but it didn't mean the writers had to like it.
How else can Bulbasaur lasting on Ash's team for more than half of Johto be explained? Instead of Heracross being Oak'd, an actual Johto Pokemon, we really should have seen Bulbasaur Oak'd.
Charizard makes its epic return for Movie 3 to battle Entei, for no other reason than fanservice for the Kanto team. Charizard returns again for Gym 8 with Snorlax, and then Squirtle makes its return for the league.
The Johto starters were like the "Tracey" of Ash's Pokemon teams. They got the same kind of reaction from the fanbase for replacing the Kanto starters as Tracey did for replacing Brock.
Its only until Hoenn began that the writers managed to get people to move on from Ash's Kanto starters, most likely because the during the Johto league the Kanto team proved their worth and satisfied the fanbase. It also certainly helps matters that the later teams actually get good development again.
