It can't, but it doesn't have to be an all-or-nothing thing. A system that is less corrupt functions more smoothly than one that is more corrupt, even if there is still corruption.

In the U.S, corruption takes the form of old-boy networks for financial access, exclusive business relationships, under-the-table deals that you'd rather not be made public, close relationships between business and politicians, alumni networks, etc. In many other countries, corruption takes the form of bribes needed to even start a business, hired goons that you have to pay off for protection, unreserved Party loyalty, and midnight executions of people who are deemed a threat. As a startup founder, I get annoyed at all the hoops I have to jump through that have little to do with building a good product, but realistically, I am risking comparatively little and there are ways to convince people that don't involve obsequiousness. Doing something disruptive in, say, sub-Saharan Africa or China or the Philippines often involves much more significant risks to life or property.

It, of course, can't be done practically speaking.

That's one of the the basic failings of all the true free market capitalists (at least the ones who really believe in it and aren't just using the idea to manipulate others the way religions do with their 'flocks').

They have this naive understanding of human nature that believes such a system could exist without corruption when history shows again and again and again (and again...) that even if you start from a system relatively free of corruption, if there are not pre-existing checks and balances (eg. meaningful government regulations) that are constantly maintained the entities who "win" at the system invariably become corrupt in order to maintain the status quo that has worked out so well for them and they begin to tilt the system in their favor. Since they won (and thus have the most resources) they are in the perfect position to influence the system to bend to them, which they invariably eventually do if given the chance.