It was in 1997 that the Pokémon animated series began airing after the successful Game Boy releases of Pokémon Red and Green. This series featured (and still features) Ash as the main character, who has been pursuing the goal of becoming a Pokémon Master ever since.
This goal was achieved, after many years, in the Pokémon Sun and Moon season, when he was crowned champion of the Pokémon League of Alola. However, despite having achieved his long-cherished goal, he is still the main character in the Pokémon Journeys series, which may lead one to think that perhaps it would be better to revamp the series with a completely new protagonist, perhaps one of the characters seen in Pokémon Sword and Shield or even a secondary character that has appeared before.
Another very good option to end Ash’s role in the Pokémon series would be through episodes in which we see him grow in age, as we should remember that he is still (mysteriously) the same age as in the first episode aired in 1997, or perhaps a season in which Ash appears as an adult, which could encourage old fans of the series to take it up again.