[Spoiler alert - I talk about the Blade Runner in this blog post.]
Filmmakers often feel like their movies must have a message.
This is not true.
However, a movie should have a point. A point does not need to be propaganda. Usually propaganda isn't as rewarding or provocative or meaningful for the audience as a would be simply a "point."
A point could be just a question, a notion, an observation.
For example - a movie with the message "war is bad" might be good intentioned, but is a little simple to be a dilemma.
The central dilemma should bring up a question that does not require and answer within the film.
For example in Blade Runner - what is message? There isn't a simple propagandistic message - but it does ask a provocative question: "What does it mean to be human? Are we human because of how we feel and that we have memories? What if you could implant that into a body - would that body become human?"
The dilemma of Blade Runner is not that Deckard has to kill a bunch of Replicants - that's the plot. The dilemma comes from the fact that he basically falls in love with a replicant - the people he is supposed to be killing. That dilemma brings rise to the "point" - which in this case is a question. We can call it the Controlling idea borrowing from essay terminology.
If you're scrīpt has no Controling Idea, it will feel empty. If it has a heavy handed message, it might feel equally flat, but people will recognize that it had a purpose.
Very often movies are generated from this controling idea as the very core of why the writing of the film happened. However, sometimes that can be lost in the effort to expand the film. Also, sometimes plot events and great moments or just the desire for a certain actor to be a certain character will be the genesis of a scrīpt. At those times, the first question might ought to be... what is the the controling idea?