Similarly, as a visual medium, showing things happening rather than explaining them has much more impact. Using dialogue (or worse, monologues) to explain something is weak storytelling; it's not making full use of the medium, and won't have the same impact as it could otherwise have. Other exposition techniques, like flashbacks, are often cheap - they can appear to make things momentous not because they're part of a story, but because they have some convenient echo in something jammed in precisely to deliver the echo.
There's much more to good movie-making: lighting, cinematography, and especially the soundscape, as technical elements that both paint beautiful pictures, and draw the viewer into the "realism" of the scene portrayed, usually by subtly overemphasizing reality.
They're definitely not half-baked ideas.
Take Fight Club as a simple example. It's both about adrenaline-pumping aggression and destruction, and a critique of masculinity. If it was only the first, it would be mindless; if it was only the second, it would be dry and boring. By combining the two, you get both juicy entertainment, and food for thought for the masses. Making something properly entertaining - more entertaining for the average viewer than e.g. a philosophy textbook - needs more than just ideas.