>>18338180The two aren't comparable. Takahashi ended his story, packed his stuff up and left, and then Konami commissioned some barely-related sequels because they wanted a Yugioh cartoon on TV so it could advertise their cards, and if the author won't write more, they'll find some new authors to do so.
The Pokemon anime isn't really based on another work (apart from the games, but their stories are quite different), and is still made by roughly the same people who were there at the beginning.