The idea that inheritance tax is a 'death tax' seems like an inaccurate pejorative. The recipient of wealth is the one being taxed, there is no extant individual whose death is being taxed. In almost all large transfers of wealth we have some amount of taxation. If inheritance tax is the exception, it encourage dynasties to hoard wealth to confer the associate power and status on their families.

This wealth would be more efficiently allocated by the innovators of new generations. It is true that the economy isn't a zero sum game, but we can't pretend that so much new pie is created each generation that dynasties hogging the majority doesn't preclude new, more innovative money, from establishing the positions they might otherwise we allowed to, for the benefit of all participants in the economy. The velocity of money matters, and allowing dynasties to guard their wealth indefinitely is bad for everyone.

This also pretends that capital confers no significant power. The reality is that the inheritors of the ultra rich will also inherit their ability to influence society. While not ideal that the ultra rich themselves have this ability to the extent that they do, to be able confer it on an almost arbitrary set of individuals is additionally hazardous, as they have not set themselves apart from other individuals on any meritorious basis.