I'll be honest: they could've implemented both the old and new systems in wild battles. Choose between fighting the Pokémon to weaken it, or immediately aiming and throwing the Poke-Ball using the Joy-Con. The more you attack the wild Pokémon, the slower the Pokémon moves when you try to catch it, thus making it easier.

They also could have implemented both RNG and overworld wild Pokémon. Just reduce the rate of RNG. Otherwise, what's the point of grass?