Two more possibilities:

- A film may have been marketed as one particular type of movie via trailers (e.g. as a horror film) but was actually a different type of movie, often a subversion of the genre it was marketed as (e.g. ended up as social commentary). So audiences feel deceived and report that in their ratings.

- Similarly, there are movies that are "applause lights" where critics are obliged to give positive ratings due to the social significance of a film (e.g. made by a woman / featuring a woman in a lead role). But the movie might just not be that good, and audiences report this in their ratings.

> social significance of a film (e.g. made by a woman / featuring a woman in a lead role)

for a less divisive example: movies about the film or theatre industry get high marks and fit your example while the audience is left scratching their heads

Excellent point. Critics have often remarked that movies about Hollywood tend to get Oscars just because of the subject matter, which Academy members like.

Also, a less cynical example: some movies are about something new: you might see people who live in a developing country, e.g., Somali fishermen in Captain Philips, or in unusual occupations (e.g., WWF wrestler in The Wrestler). Most audiences just want to relax and not learn something new, but critics love these kinds of movies.