Are you distinguishing an inheritance tax from an estate tax? Arguably the former is more fair than the latter: if a rich man bequeaths his entire estate to one child, both taxes would be the same. But if he gives much smaller amounts to many different people, the inheritance tax would be much smaller.

If your goal is to reduce dynastic wealth, this is arguably a good outcome because there's less "harm" in a bunch of people getting a smaller amount of money than a single person getting a huge amount of money.

However, things are a little less clear if a rich man gives all his money to his 4 children, their 4 spouses, and his 12 grandchildren. It still seems pretty dynastic in that case, even though the estate is being split up between 20 people.