Why have I never heard about this site until now?

It's proven very difficult to get any opinion leaders or media outlets to talk about Script Revolution. That said, some have been there to support what's happening in various ways. Simply Scripts have actively promoted what's happening here from day one while simultaneously doing their best to help screenwriters for free in their own way. Rich "RB" Botto's week end blog (well worth following) mentioned Script Revolution in the very early stages. Stuart Wright from Britflicks and Wayne Kelly from The Joined Up Writing Podcast have both conducted interviews about the platform.

Script Revolution got its first mention in a major publication five years after its launch within the following article; How Screenwriter Databases Like Coverfly and The Black List Can Find the Next Bridgerton 

If the people you look to for guidance haven't told you about this site, which is free to use, has been operating since 2016, and has plenty of success stories to its name, you need to ask yourself why that is. There's a chance they don't have your best interests at heart.