Capitalism does not allow all people to thrive and succeed. It's a system that creates haves and have nots. And there are people who will never be able to get ahead. In fact, just two things will keep people from ever being anything but bums. Those two things are laziness and stupidity.
Either one, by itself, isn't necessarily a bar to success, although either one will certainly make life difficult here in the US for those that desire a high standard of living. Those who happen to be blessed with plentiful amounts of laziness and stupidity, however, are doomed to the most meager existence. And the biggest problem in this country is that somehow we've come to believe there's something wrong with that.
If people want to cling to their laziness and stupidity, they know what they'll get and they should accept that. If they want more, then they're going to have to work on those things a bit or better yet, lose the stupid and lazy altogether. In doing so, they'll lose the bitching about "the man keeping them down", too.