Personally, I would sooner accept 90% tax to the rich&living, than 100% tax upon death.
Both are theoretical of course - there is no way to enforce them really without hurting overall society. There is also no need I think. A better solution is to make sure that wealth doesn't give too much unfair privilege, and that basic living conditions are guaranteed to everyone - we are getting closer to this every decade.
You want a situation where wealthy people build a lot more wealth than they consume. The last thing you want is for them to consume their wealth, making themselves better off but the society overall much, much poorer.
Or, maybe... if there were less of an advantage to accumulating wealth, we wouldn't destroy ourselves and the environment quite so madly while doing so. Great fortunes would not be generated, because what would the point be?
ISTM that a rich person who doesn't want her estate to be confiscated upon her death could just divide it among many heirs? If the progressive tax is not levied on the heir rather than the estate, then maybe it should be. Intentional division would destroy dynastic family wealth without wasting it on the frivolous spending of the state.
2. If the world is poorer, it will be able to afford to protect the environment less, not more. The wealthier a nation, or a neighbourhood is, the more it cares about protecting its local environment. For example, as China gets wealthier, it cares more about having cleaner air.
3. Wealth concentration in the right hands is not necessarily a bad thing. Increasing taxation is just concentrating more wealth in the hands of parliaments/governments, which they are unlikely to spend too effectively given that they are spending someone else's money, but yet which still results in some great outcomes (scientific advancements, until recently space flight etc.). Wealth concentration means that great leaps forward can happen in areas that at first are going to be very expensive (medical/longevity research, grand projects like SpaceX, even originally mobile phones etc.)
If you want to tax anything, it is probably better to tax (frivolous) consumption, i.e. wealth destruction, instead of wealth creation.
Sure, I agree, but we're talking about estate tax ITT.
It's nice to imagine that switching from income taxes to VAT (with appropriate progressive adjustments for the poor) would allow the merely hardworking rather than just the lucky and unscrupulous to accumulate wealth, but it's not clear that would be the case.
No, it would encourage people to conceal wealth transfers as consumptive spending. (Just like existing dedicated wealth transfer taxes—gift and estate taxes—do, but more strongly, and we've seen what people dedicated to transferring wealth, like Fred Trump, already do.)