Just as football has offense and defense, running and passing, screenwriting has: material, three-act structure, actions, and dialogue.
If you're competent at all of them and can keep your eye on all of them at once, you're basically doing pretty well.
If you're great at one of them, you will probably ignore your deficiencies in the other areas. Everyone's seen these scripts that have wonderful dialogue but no structure and no actions: nothing happens and you don't know where the thing is headed. This is because the writer was so fond of his own dialogue that he ignored the rest.
Most people who try to screenwrite aren't even competent at one of them. And if you don't use all of them, you can't be competent.
Material. This is the stuff of life that you know about and bring to the story world.
Woody Allen's material is being a neurotic New York Jewish intellectual. He brings that material to the future (Sleeper), the Russian Revolution (Love and Death), and even to Spain (Vicki Christina Barcelona).
Kevin Smith has his material: suburban white guys who love comic books.
