Well, you still have to pay the estate tax, but you are probably arguing that is independent as it would need to be paid regardless of the step-up in basis.

Yeah, the real loophole is step-up in basis with no corresponding tax event. What should really happen is that every step-up in basis should correspond to a tax event or, somewhat more speculatively, only net changes in basis should result in tax events. Incidentally, this would also give everybody access to reduced taxes due to unrealized losses (tax loss harvesting) instead of just people with accountants.