Call me sore loser but it can absolutely decide a match: https://replay.pokemonshowdown.com/gen8randombattle-1710357121It's not like Snow Cloak boosts accuracy by several stages; it's very manageable. With the duration of Hail (and the fact that without dynamaxing Glaceon itself, Glaceon will always, at most, benefit of it for 3-4 turns), this isn't a strategy anyone would consider unless they absolutely need to.
Yes, there will always be some element of RNG in pokemon from Focus Blasts to Scald burns, but the whole point of several Smogon clauses (Evasion, OHKO, Sleep) is making that matter less and prediction/knowledge matter more. Evasion is particularly egregious in that the attacker wastes a turn completely, and the few ways of countering evasion is very rare or limited (dynamax). Didn't Moody sets get accepted in gen 8 because it can no longer boost evasion? As for on-hit abilities, you can play around them with common moves.So yeah, Glaceon is just an extreme case whose abilities are just so bad, that a terrible ability in Snow Cloak happens to be its most viable. If we want to remove all ability-related RNG, may as well get moody out of the format (not something that I agree with, for info), and maybe flame body, static, cursed body, etc. that are all just as cheesy, if not more (due to how incredibly impactful they can be), than Snow Cloak.
This is what can and should be done. Ice Body is equally as situational without the RNG.I think they were asking for the evasion abilities to have their priority lowered to the point of never being picked for anyone, not for Ice Body to have its priority raised.