What does ‘Long on looks, short on spirit’ mean?

I wouldn't say that this exact phrase is a well-worn cliche, but the format is well known. I've also heard 'Long on style, short on substance', as well as other variations.

The meaning of each of these types of statements is to compare traits of a larger subject, especially when one trait is vastly overrepresented compared to the other, "Long on [trait A], short on [trait B]." (This is also true if one trait is vastly under-represented.)

My guess is that the character in question is physically attractive, but isn't passionate enough (emotional enough, emotive enough) for the role. Which is why the reviewer talks about missing the "the spark of rebellion" in the heroine.

Come to think of it, the phrase could also refer to the work (or a work) as a whole. Handsomely staged, but without a subversive spirit. Beautiful sets and costumes, but lacking heart. Stunning but superficial. Or something similar to similar effect.