The problem is that your loophole is my socially-significant deduction. Why wouldn’t we want to allow deductions for insulation and energy efficiency, or electric cars?

Every deduction exists because someone wants it to exist. And “eliminate all deductions” lasts until someone goes “but what about the child credit” or any other issue.

This will continue as long as Americans continue to be averse to the idea of actual cash transfers and continue to use the tax code as a backdoor system for remitting subsidies and credits.

I understood your argument to be that the rich tend to find ways to pass on their taxes, which I might even agree with--maybe, so I was thinking that if taxes don't do it then what would. I agree with my sibling though: the tax code is where we've subsidized people for generations now because of our discomfort with giving benefits to Black Americans. I think it would be hard to convert all that into equivalent benefit programs, and I think that's why people on the right advocate so much for it, because the likely end result is that many of those programs are cut, and the rich still only pay capital gains.