No. Having everyone pay the same tax rate does little or nothing to simplify taxes. The two things that makes taxes complicated are determining your income and handling deductions and credits.If we had a flat tax with no credits or deduction, it would not make it through a single session of congress without modifications.
I know almost everything there is to know, such as what causes quantum fluctuations, what you'd encounter in a black hole, how to cure cancer, how many angels can dance on the head of a pin... but I don't have the slightest understanding of what makes people so stupid. "If we just give rich people a tax cut (e.g. a "flat tax", the elimination of the higher tax brackets), then the tax code would be unalterably simple." Uh?