I think most western countries have moved away from the very high marginal tax rates. Sweden was losing doctors — not to other countries, but to hobbies. Doctors were only working half days, spending the other half doing what they really liked. When the highest marginal tax rate went from 85% to 60%, the doctors came back to work fulltime.
What is a moral tax rate is a matter of opinion. We could argue that 10% is too much. OH WAIT, THERE ARE ALREADY PEOPLE MAKING THIS ARGUMENT.
Rather the government should tax the wealthy up until the point they start withdrawing their services from the economy. That’s sort of like a business increasing its prices until it starts losing customers.