I recall reading about a concept called a "diagonal tax," which is a clumsy name, but an interesting option. Exempt all income up to a certain amount, then tax anything above that at a flat rate. It doesn't solve the issue of representation, but it simplifies things without placing a burden on the poorest people.
I understand that in some countries, taxes are simpler and assessed by the government via a straightforward calculation. The tax code in the USA is very complex, and any attempts to simplify it run afoul of the lobby for tax prep companies (which are often arms of large finance firms), which make a lot of money by navigating the complex mess of taxes for citizens. It'd be great to have a simplified tax system. What we have now is so complex that you can go to great pains to do your taxes correctly and still run afoul of the law. And the government, through the IRS, can be brutal in its treatment of citizens who underpay by even small amounts.
The same IRS, mind you, which is now the beneficiary of additional billions in government funds intended to increase its size by some 87,000 workers...