We also can’t say “Well, taxing the rich doesn’t solve everything, no use taxing the rich”. Nor can we say “Waaaah! Unfair to tax estates!” at the same time saying “Haw haw! We’ll just figure out loopholes anyway!”
I am pleased that false claims of double taxation seem to be lessening. Many times large portions or estates have never been previously taxed at all, for example on capital gains of things never sold prior to death.
We can perfectly well say “taxing the rich even at double or triple current rates won’t make much of a difference”. There is a difference between “solving everything”, “making a significant difference”, and “not making any significant difference”.
It is also perfectly reasonable to say that a proposal is both unfair and impractical.
The man who moves a mountain begins by carrying away small stones. Taxing the rich may not give us all the money we need, but it will be a start. Taxing estates higher would be another positive step. Raising taxes on upper middle class would be another. We can’t let the perfect be the enemy of the good- there are many little things that can be done that add up to a big difference.