I agree that inheritance is bad (for society AND for the recipients), but I think a lot of the issue could be addressed through social pressure to donate much of a fortune past a certain level on death (or irrevocably donate it while alive, retaining control, as a trust). Failing that, a 25-50% inheritance tax probably works, although without the free step up in basis in the current code.
On the other hand, someone inheriting $10b can do more than just live a life of leisure: that kind of multi-generational concentration of wealth significantly changes societies, producing quasi-aristocratic families that have oversized influence, and really damaging any sort of pretense to an egalitarian society with a level playing field (something Thomas Jefferson, for example, was very worried about).
So imo inheritance taxes should be mostly aimed at very large fortunes and trusts, stuff in the $100m+ range, not $5m inheritances. Other benefits are that a large exemption would avoid causing problems for inheritance of family businesses, and greatly reduce the number of people affected (which in turn should reduce administrative expenses).