Many Pokémon fans were disappointed when Ash stopped using his older Pokémon to compete in big battles. Besides Pikachu, he was only interested in winning with his most recently caught Pokémon. This was almost reasonable for League matches, but it got particularly frustrating when Ash refused to use his strongest Pokémon for the World Coronation series.
However, Ash did have his reasons for sticking with new teammates. It's all part of the fresh start he takes every time he enters a new region. He probably could do better with stronger Pokémon, but he wanted to do what he felt was right, even if it was more challenging.
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Did Ash Need His Old Pokémon to Win?
Ash's reasons for sidelining old Pokémon were revealed in Advanced Generation Episode 125, "Like a Meowth to a Flame." Professor Oak contacted him before the start of the Ever Grande Conference to see which Pokémon he would like sent over. Ash, however, had other plans.
According to Ash, coming to Hoenn was about making a fresh start for himself and Pikachu. This is why he left the rest of his team with Professor Oak in the first place. Furthermore, his then-current team worked hard to earn Ash his Gym Badges and the right to battle in the Ever Grande Conference. Thus, as much as he might have liked to use Charizard or any of his other veteran Pokémon, he was committed to using his new team to win.
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Of course, Ash would shelve this ideology after this League was over. He went back to using older Pokémon for his Battle Frontier challenge whenever he felt they’d be useful. He still mostly relied on his Hoenn team to earn his Symbols, but his old Pokémon were there when he needed them.
Ash followed a similar mindset when he competed in the Sinnoh League. He relied exclusively on Pikachu and the Pokémon he caught in Sinnoh to earn his eight Badges. At the Lily of the Valley Conference, however, he was more than happy to use whatever former team member he thought would be helpful in each match.
From the Unova League onward, Ash reverted to his Hoenn League methods and stuck with them. This was especially frustrating when he lost in the Lumiose Conference finals; this was the furthest he'd ever gotten in a League. He did, however, win the Manalo Conference and the World Coronation series without any old Pokémon. It took a while, but his self-imposed rule finally paid off.
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Should Ash Have Used His Old Pokémon to Win?
Fans, however, still wish Ash had used at least one of his older Pokémon to win the World Coronation Series. These world-ranked matches were supposed to be Ash's biggest, most challenging matches ever. If he wanted to use more recent catches, that was fine as long as they were strong. Winning, however, should have motivated him to bring out his strongest possible team. This is to say nothing of Pokémon Journeys being Ash's final series as the protagonist; it would have been the perfect place to showcase the Trainer at his full potential. The fact that he stuck with an entirely new team, even in this scenario, is one of the anime's biggest missed opportunities. As cool as it would have been to see Ash put together a dream team, it was never meant to be. After Johto, he was determined to give his new Pokémon a chance to prove themselves. It worked out in the end, and he eventually became World Champion, but fans will always wish they could have seen the day when Pikachu, Charizard, Sceptile, and Greninja were all fighting on the same team.
