The people themselves don't pay the estate tax anyway, it's their children. And none of that money is something they "earned", and the first 3.5 million are still untaxed. If somebody gave you over 3.5 million dollars and you complained that it's not more, then you'd be incredibly spoiled (I don't think you would)
When there's unjustified loopholes, we should close them. Either way, the estate tax does create some revenue, 19 billion in 2014, when the threshold was 5.34 million. Now imagine we start taxing at 3.5 million, and we make the top marginal estate tax rate not 40% as it was then but Bernie's 77%. Quite some revenue, "taken" exclusively from spoiled brats