So is there really no reasonable way to gain XP/EVs this time around? Or is Poke Pelago supposed to be the go-to training method?

If it is, I can't tell what the fuck Gamefreak is thinking. Do they really expect people to wait hundreds of hours to max out their Gen VII shitmons? Kids are impatient and competitive players are just going to cheat anyways, so it doesn't make sense if this is part of a plan to increase the games' longevity.