Sales taxes come out of the income you already pay income tax on. Property taxes ditto, except you also already paid property taxes last year on the same damn property, and will again next year! This is much worse on the double taxation angle than the estate tax IMO. Not to mention, again, that the step up in basis exists explicitly in defiance of the double taxation complaint.
Property taxes are a bit easier to justify on a practical basis, funding for local governments has to come from somewhere and charging residents within that government's jurisdiction an annual fee is probably the most reasonable solution. If you don't like city taxes you can just move out to an unincorporated area without any of the benefits of city services.
I agree with you on sales taxes, however.
I suspect we just disagree at a conceptual level about what is "equal burden". Is it 30% of your money? Or 30% of the money you didn't spend on bare survival? What is bare survival anyway? These are hard questions to fully answer, maybe even impossible, but it seems evident to me that after accounting for health care, living space, transportation, and food the pie is a lot smaller compared to how it started on one side than the other.
I'm not really seeing how this is confusing, the concept of a flat tax rate is extremely simple. It's understandable to exempt some people from it because they're below the poverty threshold, but past that point the concept is simple enough.