The movie may not have been earth shattering, and it may not have told a timeless tale,  It lacked true significance.

The author of the review did not pick a great word when the movie was called ''slight''.  This was perhaps intentional and a play on the word.  The reviewer was "slighting'' the movie.  To slight something is to say something negative about something or fail to acknowledge any of the good points. 

An awards presentation can slight a movie by not nominating for an award. 

Perhaps it is a combination of a pun and an insult.  The word may also have been a typographic error or a replacement word by an editor removing an offensive word.

The context is " It was, in many ways,a slight movie.Nothing actually happened.There was no big-budget chase scene, no bloody shoot-out.The story ended without any cosmic conclusions"  can you help me ?

  Antonyms  are words with opposite meanings.  Hot/Cold,    Friendly /  Hostile,

Anxious / Calm,   Positive / Negative

   Synonyms are words with same or Similar meanings.

 I am usure about a  movie described as  "slight".  Do you have other information?

From Chambers Dictionary:

Slight: lacking substance or value • <em>slight works of literature</em>. (One of several meanings)