Nah, Lillie got plenty of development throughout Sun and Moon, it just didn't get any notable payoff at the league itself where her battle was far too short to do anything, her Z-Move did absolutely nothing, and the combination of Aurora Veil and Snow Cloak, which is actually a very good defensive combo, was beaten not by any sort of skill from Gladion but by the hail ending very quickly before the combo even got off the ground. My issue is not with the season development, only with the payoff at the end. Gladion also didn't get the opportunity to show off any skill in that battle either, but his situation isn't as bad as he got plenty of opportunity to be cool in later battles, particularly against Kiawe and Ash.