Would guess the idea is more about who pays that similar revenue, as since the 80s income inequality has shot upwards.

You are talking about revenue neutral at a population level. What matters to individuals is their own revenue. The impact of these changes on individuals varied a great deal. Many middle class lost valuable deductions while wealthy people saw their rate drop dramatically. There is absolutely nothing remotely neutral about any of that. So the only context where neutrality can be asserted is the same one where the statistician drowns in a lake that is an average of less than three feet deep.