I need a clean site that allows users to create content, and have it added to the website's content database, let them share, etc. It doesn't need member/login functions. A good comparison would be a meme generator, something like that, except instead of downloading an image, the content the user makes is turned into a web page, not temporary, but permanent.
Really it probably isn't the most complex backend, as it revolves around 1 simple backend function, but I don't want to share all details of the site yet.
Also advice on which platform to build the site on is appreciated. I'm thinking Joomla, but I really have no clue. Ideally this will be a rapidly expanding site in terms of size, simply because there will be lots of user created content that will be featured on individual webpages.