That's the way the system works. Every once in a while a third party makes and appearance but, in a winner takes system, that person acts as a spoiler for one of the two major party candidates.
It takes a lot of work, and support to get on the ballot in the states. Different states have different rules. Next, it takes at least $150million dollars to even be competitive. Campaign donations are limited per individual and political action organization. The two major parties candidates have their party and political organizations running supportive campaigns, commercials, ads, etc.
We don't have proportional representation, which would make a difference. And, we don't have public financing which means a very few would even be able to entertain a run.
But, did you say 'russian democracy'?