You literally can’t! Or underthink it, lol. If that’s the meaning you take from the work, that’s what it means to you.

More or better evidence of the meaning might strengthen your position but viewer response as an idea is inherently individualistic.

Does that mean that, say, Starship Troopers is just about squashing bugs? Well, not really, but it doesn’t mean those people didn’t enjoy an simple action movie, no notes.