You'd also be surprised at the number of companies out there that aren't the Big Five and are tackling a bunch of interesting problems using different technologies.
This. And what everyone else is pretty much saying. If you only read tech blogs you'd probably think the only companies in existence are Google, Facebook, Amazon, Apple, etc. The world is big and you can have an impact in places that will probably never get press, because they aren't sexy enough. Take healthcare, Google keeps trying to break into that industry, and kinda failing miserably. Partially because the problems in that industry are more related to regulations and people, stuff that machine learning isn't going to solve anytime soon.