Ahhh.....Therein lies the primary problem in my eyes. The execution is the complexity and inequity!
Due to all of the other retirement programs in place such as IRA's, Roth's, 401k"s to name a few, one can manipulate those income streams to the point where their SS benefits are not taxed at all. Another person living the same lifestyle with the same retirement income, with the same SS benefit may be paying taxes on 85% of their SS benefit. i.e. The complexity becomes huge when working between all the other retirement plans/programs. To those people not willing, incapable or unable to optimize those variables, taxing some people's SS at multiple levels becomes complicated and an unfair policy.
Taxing SS benefits has unintended consequences. For me personally, those consequences make it complicated. And if it is complicated for me, I assume that there may be others who are also going thru that same "experience", probably more than a couple of people. in my mind, if SS was not taxed there would be no complexity.