Absolutely. But really there should not be capital gains tax as it is double taxation - you have already paid income tax on the same dollar.
There are good arguments against capital gains tax, but this is not one of them.
If you invest a dollar today and get ten dollars tomorrow you’ve gained 9 dollars. When were you taxed for that?
If I invest $100 (post-tax money) and sell the investment at $1000, I do not pay taxes on that $100. There is no double taxing. I do pay taxes on the $900 gain.
There is no double taxation here.
There is a more nuanced question as to whether or not inflation should be incorporated into the calculations, but there are pros and cons there also.