I hear this a lot, expressed in many different ways; It's been done before, I've seen this but a little different, This reminds me of that one thing, So and so is already doing something similar.
This is a lonely sandbox to play in, isn't it? I think this is oxymoronic. Ideas beget ideas. Perhaps the real point of interest is, we're exposed to more ideas and communication than ever before in history. Not that lots of ideas and notions haven't been thought of in previous years.
Today we have direct access to a lot of content. And while ideas borrow from ideas, there will always be originality. So it may appear that everything has been done before (the lonely sandbox), but questioning the propensity of originality is analogous to suggesting that a wade of clay will always end up the same shaped ceramic.
Turn off all the content long enough to think about what it is you're thinking about. Spend time on iterative design, thinking and exploration. It's okay to be a little like something else, too. Technique is making a perfect mistake. It has nothing to do with talent.