Capitalism is not as much about the channeling of greed as it is about the competition of ideas. Government and bureaucracy thwart ideas. Capitalism works best when knowledge and power converge. Hundreds of financial regulatory agencies failed to avert the economic collapse of 2008 because they wielded power without knowledge.
Hubris and power often undoes itself by reaching too far. Never satisfied with the power it has, it seeks more. Policy failures are not faced honestly, but blamed on the restrictions that power faces, such as the Constitution or the Bill of Rights. Thus they seek to subvert the restrictions of constitutional law, or any form of accountability, to fulfill their moral supremacist and utopian fantasies. In the heart of every moral supremacist is a wish for a benevolent dictator, unrestrained by limits on their power. But when the dictator is no longer benevolent, he is still a dictator.
The tragic hidden cost of regulations is that in the effort to avoid the pain of small failures we also stop the construction of firewalls that would avoid large failures. Secondly, we miss the value of failures in ultimately achieving success and innovation and thus inadvertently miss out on opportunities and new discoveries. This combination of outcomes increases the downside and restrains the upside.
The point here is that it really unnecessary for the government to seek estate taxes to restore fairness in the distribution of wealth; the normal path of family and wealth evolution seems to accomplish this task on its own.