There's something in this movie which make it stand apart from other MGM musicals of that period, and I believe it was precisely this reason the movie ended up as a marketing flop.
First of all, the whole movie has very exaggerated and stylized tone, which combined with the vivid cinematography of Vincente Minnelli, creates rather fantastical, storybook-like (remember the movie actually starts with turning of storybook pages) mood, which might feel too alien to the audiences who expected to see another typical MGM musical like For Me and My Gal.
Of course, other period musicals like Meet Me in St.Louis or The Harvey Girls are far from realistic also. But while we can say that Esther's family or the Harvey House in those are rather idealized or exaggerated, they are by no means fantastic or surrealistic like such an imaginary Caribbean island where things like a pirate in his hot pants cutting ears off a bunny hat look like 'normal'.
If such an intention can be misinterpreted even by a modern reviewer to make him to criticize the movie, based on ethnic demography of a typical Caribbean island, then it's hardly surprising to see why some audiences from the 40s found it to be 'over dramatic' or 'over the top', for example.
As to the movie itself, I think I should give more credit to Gene Kelly than to Judy Garland even though I'm a big fan of the latter, and actually it was because of her that I first decided to watch this movie.
Aside from the "Mack the Black" or "Be a Clown" numbers, which are nice but can't be said to be top notch, music scores of the movie aren't very impressive, so regretfully we don't have much occasion to appreciate Judy Garland's legendary talent.
But as to Gene Kelly, the movie serves as a great showcase to prove that he's much more than a mere good looking actor with some tap dancing skills. By adapting elements of ballet or even pole dancing, he tries to innovate the musical dancing to a whole new level, and sequences like "Nina" or the "Pirate Ballet" feels like a precursor to his later efforts which successfully enlarged and redefined the field.
All in all, it's one of those movies which can be termed as a 'successful failure', which was successful in making a lasting impression with many bold and innovative attempts, and be a marketing flop for the very same reason.
If there were a bit more memorable music numbers, which would give Judy Garland more chance to shine, it might have been remembered as one of a cult classic of MGM musicals.
