Technology is a marvelous thing. With the progression of blue or green screen technology, motion capture, and the aid of computer graphics and effects - concepts, ideas, and stories that were once impossible to put on film have become the reality of modern filmmaking.
There is always a way. Don’t let anything stifle your creativity when it comes to screenwriting. Write the type of movie that you yourself would want to see and don’t let technical aspects shape your story in any way. Make them work for you, not dictate how you must work.
Remember, story is more important that visual effects. At the end of the day, it's all about what happens to your characters, how they react, and what they'll do about it - that matters.
Make your story so compelling, so irresistible, that producers absolutely have to make it!