>>38365361I believe Festival Plaza set maximum levels, so you couldn't keep feeding your pokémon there until level 100.
The best way to do it in USUM was with chansey chaining, and it was admittedly fast, but it required a lot of abstract knowledge about chaining and the specific features of this specific pokémon; after insisting game after game that trainer pokemon are stronger and give more exp. Which is how they handle breeding, so it goes to show that they just did a quick patch to a problem they dug themselves into instead of fully developing a solution, as it happened to most of SM's issues going into USUM.
Which is stupid, because a quicker and more effective patch was as easy as just removing the level 100 requirement from hyper training (although the birs and larvesta would still be a pain). It's already locked in the postgame, what's the level 100 even for?
At any rate, out of two gens they've tried this exp scaling thing, both have needed a retry to unfuck things. I don't think next time they'll get it right on the first try either.