I found a book called 1001 Movies You Must See Before You Die, and it pretty much confirmed that critics just haven't quite known exactly what to make of this film. It's so bright and boisterous on one hand, and then we see the Halloween scene and Tootie crying along to Have Yourself A Merry Little Christmas and we don't know quite what to think.

MMISL is from the age of "humanism", whereas most movies after the 1950's and beyond are considered "post-structuralist." Films made prior the onset of post structuralism took quite a different approach to film theory. There are obviously many elements to this, but, in the humanist view, each film is a work of art in itself, and thus the amount of analysis that goes into each particular film is quite extensive. Films from the post-structuralist era are not concerned with evaluating each and every nuance involved in dialogue, scenery, and every other nuance that goes into the film; they are instead focused on the particular film's relation to the themes and ideas that exist in the art/film world as a whole at that moment. Films in the post-struc world are concerned with adding to the always expanding field of ideas and themes that further a rather particular discourse -- that discourse, generally consists of ideas that stem from "post-structuralist" thought, which is very similar to "existentialist" and "post-modernist" thought. MMISL and films from the humanist age, on the contrary, are not necessarily evaluated based on their relation and contribution to the other prominent ideas and themes of the day, but instead every speck of possible evaluation and analysis from a film in the humanist age must be exercised, despite the fact that many of these themes and messages might have little meaning and little to say to no one in particular...It's quite tiresome, yes, but tis the nature of (some) classic movies, and some contemporary movies as well. Many elements of the "humanist" or "realist" age still exist in the post-structuralism world, much to the chagrin of many post-struc ideologues.