Pokemon has always been designed around player interaction, even back when you needed a Link Cable for it. In the modern world, that means being able to battle just about anyone around the world, so the competitive balance needs to be properly considered.
On the other hand, though, the mainline games have also always been single player experinces that offered plenty even to a player on a lunar mission. Maybe there is room for a “game” where you just raise Pokemon for online battle, but that should be one of the zillion spinoffs.