Screenwriting in today's market is a bit different than it was a decade or two ago. You can no longer expect what you once could. Many of the myth's about get rich quick by writing a killer screenplay are from some years ago, as myths are wont to do, dwell on long after they happened and are no longer relevant.
As always but now more than ever, a writer needs, if they want to make it as a full time professional, to be a jack of all trades and master of all of them. Consider this:
Consider your emails, what if you had to read all the spam that comes across every day without using any filtering software? I have had one of my email accounts since about 1995. I get a lot of spam. But if I didn't filter, I'd never see the important emails I really care about. It's much the same with scripts. You have to filter out the fluff and riff raff to get to the quality stuff.
And so, your script has to stand out. That first page has to explode.
You also have to diversify. There's two reasons for this. One, is that you have to be prepared to answer when opportunity knocks, whether it is for screenplays, or any other form of writing. Two, you have to be versatile. Versatility gives you more range in your screenwriting. That means, you have to not only write as much as possible, certainly on a daily basis, but you also have to read, as voraciously as possible. When you're not reading (fiction, books on writing, history), you should be watching movies, examining what works, what doesn't what you can use, what you shouldn't.
In the end, if you feel like becoming a screenwriter, and this goes for most writing areas, you have to stand out; and to stand out, you have to earn that standing by being extraordinary. Do more work than other writers. Do it as a profession, not a hobby. Do it as a Zen Monk, make it the end all be all of your life; at least until you get somewhere.
It took not only writing for years off and on, but contacting people over the years, giving me references to go back on, name drop, have an attitude of already being what I wanted to be, to get people's attention. Once you have done the work, you have to have a presence available for people to "see" you, know about you, hear about you. Then when you are in contact with people, you have to make them want contact with you, to hold that contact with you and to want to contact you again.
Someone said once that in pitch meetings you are selling yourself, not just your script. You have to let them know they will enjoy working with you, you can handle what they throw at you, you can persevere and produce again and again.
And if you can get all that done, you can make it. Just remember one thing, its a marathon, not a sprint.