to begin with, people who save and accumulate wealth would not being taxes on all their income. Encouraging people to save, while prudent, does not create economic growth
people at the other end of the spectrum would start paying a higher % of the overall tax burden as the money spent on basic necessities won't have the same deviation as the tax on income does
and people who already paid taxes on their income would be taxed again on that same income when they spend it, while people who already spent their income won't suffer the same consequences
I'm not going to defend the current tax code, it's a crock of shit being stirred and stirred and stirred again by incompetent politicians, but a simplified and fair income tax system would be the most prudent way for the government to raise moneys.
Now, if we ever stop growing the size of government at much quicker rates than population growth and economic growth, we wouldn't have to continuously look for new and more and never ending tax increases.
PS: no matter what tax code changes are made, somebody will come around and make more changes after the election cycle. It's what they do, it justifies their existence