I really like this, actually. Ash went from a 10 years old who mostly had badges handed to him and wasn't skilled in the slightest as a trainer, to a 10 years old trainer who pulls the best out of even his weakest Pokémon. A prime example of this is how his Charizard, arguably his strongest base-form Pokémon, had lots of troubles facing Articuno in Battle Frontier, but seasons later he managed to overcome Zapdos with a recently evolved Noivern, by overpowering it? No, by outwitting and using of excellent strategy. (Yes, I do recognize that Articuno had a trainer, while Zapdos was wild, but still.)
At this point, I'd be glad to see Ash's rematches with members from Elite Four that he lost to. How cool would it be to see Ash face-off against the likes of Lorelei, Agatha, and Flint again? Or best-case scenario, winning against them. We have been shown that Ash went face-to-face against Alain, whose Charizard managed to overpower Malva's Ace, it's already time we see Ash showing just how skilled he is as a trainer by beating one Elite Four himself. And once the inevitable final battle against Leon comes, finally make a huge part of the fandom acknowledge Ash as an actual trainer on par with the strongest and most skilled trainers in the franchise, like Manga Red.