I am of the opinion(not necessarily strongly right now, its what i'm discussing it for). that this ability is simply uncompetitive. Looking at wcop replays, band aerilate is fairly common in a lot of mus for good reason: Insanely strong flying stab is fairly stupid and constricts teambuilding. In the replays,
here,
here, and to a lesser extent
here you can see what happens to bulky teams when they dont bring an aerilate resist. On some types, thats not a problem(steel, flying, elec) but not even talking about types weak to flying stab(where even the most bulky neutralities get 2hko'd), water makes a nice example as it basically mandates you use 1 of rotom w or empoleon for a banded aerilate mon to not get a kill every time it comes in on a bulky build. Scald doesn't work because they just carry facade and fuck shit up even more.
No ate- has such widespread abusers like aerilate:
Aerilate - Landot, Lando, Gyarados, Salamence, Thundurus, Celesteela(maybe more i'm forgetting)
Refridgerate - Weavile, mamo(maybe?), Zeraora, Lucario - None of these are problematic for most types to deal with besides ones you'd expect(flying). Theres still countermeasures(delta stream, thick fat).
Pixilate - Koko(I'll get into that in a sec), Bulu, Entei - Bulu is not a problem due to its fairly slow speed tier. Its stabs are resisted by a decent amount of mons. Again entei can be handled by most types fairly easily.
Galvanize, Lucario - Koko, Zera, - again off the top of my head so i might be forgetting, but just use a bulky ground type lol.
In theory, a meta in which this is banned allows grass to actually become a good type. Flying remains a strong type. I think bug and fighting would become more widely used as well.I'm not decided for sure if aerilate deserves the ban but conceptually, i think thats a better metagame for sure.