I certainly wouldn't agree with elements from the mini land being incorporated into Epcot's 'France', which includes the attraction itself. They are all grounded in fantasy, which is fine, but the World Showcase isn't the place for that.
I find it hard to see how anyone can come away with a negative impression of Ratatouille, though (my objection isn't related to the ride quality) - even if you have experienced Mystic Manor (which I don't dispute is leagues ahead creatively). The fact that another attraction is much better doesn't diminish the high bar attained by another attraction; the criticism would have more grounding if they shared thematic commonalities but about the only thing shared is the ride technology.
I'll be very interested to read WDWFigment's (typically!) well reasoned opinion when it's published, though!