When I was younger, naive, and more of a snob, I approached my screenwriting career in the following way: I wrote what I was passionate about and assumed that something would eventually get made. Whenever someone suggested "writing for the market," I thought of it as a waste of time. After all, if you're not passionate about what you're writing, that lack of passion will come across. Right?
Now that I'm much older and a bit wiser, I know that it's about one thing: getting a movie made. And the sad reality is a movie doesn't get made because the script is great, it gets made because it's what the financier is looking for. So here is my advice to screenwriters who are reading this: If you know a producer who owns a gorilla suit and wants to produce a monster movie featuring that suit, don't send him "Citizen Kane." Most likely, he'll say, "this is a great script. But where's the fucking gorilla?" So write something for your producer. Get your name on a movie. Then you can do something good.