not at all.
some guy who busts his hump for $25k a year has to pay 25% of his income, making him choose between getting his car fixed or stashing a little away for his kid's college.
some other guy busts his hump for $20 million a year has to pay 25% of his income, making him choose between nothing whatsoever.
the tax code is necessarily complicated, but a lot of it favors someone like the guy making 20 million so that he can pay half of what the guy making $25 does.
even a fair tax comes closer, but is still not as progressive a tax as is needed to prevent a plutocracy.