I thought it was great that you actually compared Pokemon with both a show that targets the same audience (Doraemon) and other anime adaptations of games. I agree that an anime like Pokemon, that has an established continuity, feels awfully weird for not feeling like it's moving forward with development.
Though, if not the Kanto League (where Red's journey in the games end), I thought an appropriate point to end Satoshi's journey was the Jouto League. As you said, each generation of games is unrelated to the last, except the Generation II games which are sequels to the Generation I games. I thought the anime was trying to make a parallel to the games in that sense (despite Gold/Hibiki being the new protagonist and Red becoming the final obstacle), and I honestly think Satoshi's development had grown enough there to just let him win the league and start with a new protagonist for Advanced Generation. Satoshi's battle with Shigeru felt like a Pokemon game's "final Champion battle" (Orange Archipelago too, maybe; I just think a battle with Shigeru was greatly needed as a conclusion), greatly mirroring the battle between Red and Green in the games. If it had ended there as the final round, like the final chapter of the Red and Green arc from Pokemon Special, I would have been satisfied.
I also think a problem lies within the fact that Pokemon, unlike other game-based anime, ended up being a smash hit. Even with anime like Disgaea or Tales of Symphonia, which end at the point the corresponding game ends, features drastic alterations from the source material more often than not (a reason I don't know why; it might be because of limited episode budget or simply choice of direction). If they became long-runners like Pokemon, maybe they would have had the same static character development.
Though, if not the Kanto League (where Red's journey in the games end), I thought an appropriate point to end Satoshi's journey was the Jouto League. As you said, each generation of games is unrelated to the last, except the Generation II games which are sequels to the Generation I games. I thought the anime was trying to make a parallel to the games in that sense (despite Gold/Hibiki being the new protagonist and Red becoming the final obstacle), and I honestly think Satoshi's development had grown enough there to just let him win the league and start with a new protagonist for Advanced Generation. Satoshi's battle with Shigeru felt like a Pokemon game's "final Champion battle" (Orange Archipelago too, maybe; I just think a battle with Shigeru was greatly needed as a conclusion), greatly mirroring the battle between Red and Green in the games. If it had ended there as the final round, like the final chapter of the Red and Green arc from Pokemon Special, I would have been satisfied.
I also think a problem lies within the fact that Pokemon, unlike other game-based anime, ended up being a smash hit. Even with anime like Disgaea or Tales of Symphonia, which end at the point the corresponding game ends, features drastic alterations from the source material more often than not (a reason I don't know why; it might be because of limited episode budget or simply choice of direction). If they became long-runners like Pokemon, maybe they would have had the same static character development.