Most critics like Castle in the Sky, and the praise gathers around the same things: the flying sequences, the faux-Victorian machinery and steam-driven contraptions, the droll air pirates, and a first act that several reviewers admire for how briskly it gets the story moving. Many treat it as early Miyazaki, a film whose invention points towards what he would do later. Several call it his most straightforwardly enjoyable adventure, and its balance of action and quieter passages comes up more than once.
The reservations are mild and consistent. A few reviewers find it more formulaic and less thematically rich than the later Ghibli films, and Colonel Muska is noted as an unusually conventional villain for this director. The New York Times worries that two hours may test both adults’ patience and children’s attention. The spread is narrow but for one outlier: the Los Angeles Times, reviewing in 1987, dismisses it as a generic anime adventure with sleepy pacing and clumsy dialogue, a view no later critic shares.