>>57367729During the main game, Kalos at least gets a pass because it really is that easy. Two megas for free that will clear most everything, leaving the rest for your actual starter? Insane levels of carrying. Greninja+Charizard+Lucario sweeps Kalos wholesale.
As for gens 7-9, the stories themselves doesn't give a reason for the party-wide xp share to be annoying beyond possibly making it harder to play with level caps, which are a self-imposed challenge and thus not actually relevant. If anything, Alola is benefited from it in the USUM games through the U-Necrozma fight where it has +1 in every stat, even if a Zorua can btfo it, because that's more dedication than what most players will bring to it. Nothing in the switch era games comes close, i feel, as I personally have beaten SV like 3 times with my unbred shitmons. Gallade and Gardevoir turned out OP my second time through.