im gonna have to agree with @Commander on this one, not only that but there's also the problem regarding things like hazards.
ysee, due to programming, it's hard to even program an ai to properly use hazard moves or status moves properly, and as a result, the inclusion of status moves could make a fight easier than it would be due to the fact that the ai might keep stealth rocking, or toxic spiking, making the fight easier than it really would be
not only that but the pokemon dont really make sense like i said. why on earth would venam go all the way to alola just to catch a nihilego? not to mention that, nihilego is a rather recent species that could be considered classified since it's basically an alien from another world. what im trying to say is that the inclusion of legendaries is ridiculous because it's hard to justify why they would have them in the first place. maybe genesect if it involved them with an organization, like plasma, but that's pretty much all i could think of.