Screenwriters should definitely use social media to connect with other writers. These events are great for all of those things, but they also might lead to some career opportunities you wouldn't have had before. Maybe you can't escape the excruciating fear of rejection and need a few words of encouragement. Maybe you want some script coverage but need some recommendations on who to buy it from. Maybe you're wondering which literary agencies you should seek out to get repped. Not only that, but everyone's there for the same reason: to make connections and ask/answer questions. Writing events, like ScreenCraft Summit, give screenwriters like you a chance to rub elbows with a lot of people in the community at once. In fact, for those who are just starting out, that might be the easiest (and maybe, for a while, the only) way to get "in the room" with a manager, agent, or studio executive, so that's another reason to consider entering your script into a competition. The selling point of many writing competitions is the panel of judges they feature because that means someone who's interested in mentoring or shepherding a budding career is willing to read great scripts that come through. This is why competitions, screenwriting events, and community groups are so important - they put you in the same "room" not only with fellow screenwriters who are working toward the same goals you are but also with industry professionals who can take you where you need to go in your career. Network like your career depends on it, because it kind of does. Seek out the ones coming from the most experienced, informed professionals.
However, there are plenty of companies that provide professional script analysis from professional readers, like WeScreenplay, Shore Scripts, Launch Pad, and, of course, ScreenCraft. But remember - everybody has opinions. Readers can be interns or assistants at studios, but chances are cold queries, or sending out unsolicited requests for a read, won't lead to much.
When you're sure it's a blockbuster just waiting to be produced, get it read by a reputable, experienced Hollywood reader.
Then read blogs, books, and quotes about screenwriting and revise your screenplay again. This means re-writing and rewriting again (and again.and then probably several more times). So, look yourself in the mirror and say this out loud: "It's time to improve this thing." Well, the truth is that it's going to go through many rewrites before it ever sees production. "I know, but my screenplay is already perfectly awesome," you say. Enter Now | Final Deadline in 13 hours Get Your Screenplay into the Best Shape Possible Rewrite Your Screenplay (Like.A Lot)