Most critics like it, and several treat it as the point at which Disney animation recovered its nerve. The praise clusters on the music: Alan Menken’s score and Howard Ashman’s lyrics come up repeatedly, and “Under the Sea” is named more often than any other sequence. The animation is called lush and fluid, and Ursula’s design is picked out as the visual high point by more than one reviewer.
The reservations are about story rather than surface. Empire finds the prince dull and the ending hurried, and Collider agrees the storytelling is the weak part while judging the charm enough to carry it. The AV Club, though warm, calls the film thin. The one real dissent comes from Slant Magazine, which finds it calculated and cloying, though even there Ursula is welcomed as relief. The spread is otherwise narrow; nobody argues it is less than good entertainment.