I've actually seen people cite glaceon as one of the pokemon with disappointing shinies that don't change enough

I actually really like glaceon's shiny. The main colour isn't shifted that much in an absolute sense, but it takes an already light colour lighter so it becomes more like "white with a very slight blue tint" as opposed to "very light blue". And making the blue accents on the paws etc a brighter blue is a nice contrast against the white, since you sort of "lose" the primary blue

Idk like, it is a little subtle compared to some other changes but i think the small changes go a long long way personally