Why is it so difficult to implement a follower Pokémon- NOT all Pokémon can follow you, I know GF is incapable of that much effort.

I mean just even a small pool of small first evolution Pokémon who you can choose in conjunction with a party of 6, you don’t even necessarily have to use them in battle a la LGPE just a little partner mon to follow you around, I for example would like a murkrow