There can be broadly two groups of screenwriters-first,the group that continues to turn out unusable screenplays and second,the group of successful screenwriters. Then what are the fundamental differences between these two groups in the world of screenplays.
The first difference is the desire to do it, and keep on doing it, even when the writing is not working. This is the passion for communicating and sharing a vision, which is one of the benchmarks of creative activity.
The sesond difference is the ability to learn from others. This can be achieved by study, taking feddback, discussion, or a combination of all three. The point is that it is an on-going process and each screenplay is aimed at being improvement on the last.
The third difference is the acquisition of skills and their application in a rigorous and creative way.
The fourth is time. It takes time to write and it takes even more time to write well. It can take years to write well within the strict parameters of a screenplay.
The fifth is persistence. A screenwriter has to be able to keep going with their ideas and deal with rejection and uncertainty of the whole affair.
Last, and by no means the least is the passion for the medium and the stories, characters and themes which are fundamental to any screenplay.