I like whatever gives me an exciting and challenging battle against a strong but properly balanced trainer. Consider Trials actually better implemented and I think they make more sense and integrate better with the story. Totem battles were an interesting twist I personally liked.
The concept of "Gyms" that are actually more like fun houses with dumb puzzles that have nothing to do with Pokémon hasn't aged well to me. If they're called gyms they should be more like actual gyms, or get replaced with arenas or something else.
I would like to see them getting a more "serious" treatment, giving leaders better teams and strategies, force battle Set, equal levels, more held items, remove trainer items for both player trainer and AI, etc. As long as I get a good battle that requires some strategy, and not just mashing super effective move against everything I don't really care if it's a Gym, a Trial, a Tournament or whatever else.