While it's not necessary to say "the only country" I think it IS necessary to "brainwash" people by potentially lying to them that it is possible to have econom

While it's not necessary to say "the only country" I think it IS necessary to "brainwash" people by potentially lying to them that it is possible to have economic mobility in order to actually enable it. If most people don't believe that they can have economic mobility then they simply won't even bother. In order to get many people to bother and try you need to convince everyone that it's possible, even if, in practice, few will manage to. It's a first step, a stepping stone. Of course, besides convincing people that it's possible you need to have an economy that makes it possible. So that would be the second step.