Been a while since I've played a new one so forgive me if these have been addressed already, but the two off the top of my head would be
1. Stop making trainers battle with single type teams. It's boring, and nonsensical. Using only one type makes you weak by default.
And
2. Don't tell me what Pokémon the trainer will switch to before he actually switches, giving me the chance to just throw out the perfect counter every time