No, it's not open to everyone, there is a creative discord that only certain people have access to.
Also, this is the official form you need to fill in if you want to apply for a map to be featured or a block creation. Not everyone is on reddit or on social media.
If you make a valid submission via the form, you will be added to the Creative server. The public Discord server is at http://discord.gg/fornite and it has some Creative channels.