A film like this (or something like ‘Lawrence of Arabia’ for example) should be taken in the same light as Shakespeare’s history plays. There are also anachronisms in Shakespeare that both he and his audience were well aware of. ‘Meet Me in St Louis’ is an American classic and goes well beyond the pretentious moron demographic.
If it's [mis]represented as history, it can be criticized on that basis.
Meet Me in St. Louis is a musical. Like all musicals, it appeals to morons. So its demographic includes both the pretentious, and the nonpretentious kinds.