A professional is somebody that can produce a high quality product. A professional is not an audience, and when he views things, he looks for what's good in them and neglects the poor, low‑grade things. The reason he does this is so he has an ideal scene. Without an ideal scene, he just operates off technical data and produces, artwise, a low quality product and isn't a professional. Without an ideal scene, he can never get a preconception of the shot.
In viewing things that approach an ideal scene, the true professional works out how they did it and when presented with similar tasks of production, can bring off things which approach an ideal scene in his own work.
Another thing that separates a member of the audience from a professional is that the professional only thinks in terms of getting out an actual product. It never enters his head that he's just there for the ride or that being an "expert" is enough. A member of the audience has no faintest concept or idea of getting out a product.
A professional knows the rules of the game as a matter of course so that he can achieve in the upper strata above that, a high quality of art.
When a person simply looks at everything as to whether he "likes them" or "not likes them," he's just an audience and he's on the wrong side of the footlights.
This applies to a writer, a director, an actor, a cameraman, a makeup man, a props man, a wardrobe man, a producer, an artist, any professional.
Without this viewpoint, he never accumulates ideal scenes, so how could he produce anything good? He never has a memory library to compare his own products to.
Be a professional.