Well you can define income that way, but it would be wrong. See the excellent post by nametag. Once you know your income, taxes are easy. The hard part is knowing what your income is. That’s what takes accountants and that is always going to need people at the IRS.
If all you have is income from wages your taxes are simple already. It should take you 10 minutes. It gets complicated if you own a business, do consulting, have income property, etc. And it’s not just taking your expenses and subtracting them from your revenue. Imagine you own a factory and have 1$ of income (real income, not revenue) and you buy a $5M piece of equipment. Do you just deduct that expense the year you buy it? No, that would be stupid. You would have no tax liability that first year and then pay taxes the following years without the ability to deduct the other $4M in expenses. That’s why we have rules about amortizing capital costs, depreciation, etc. That’s the shit that makes stuff complicated.
Should we get rid of loopholes that specifically target certain industries or individuals? Of course, but ridding the tax code of loopholes would only eliminate a portion of the costs of accounting and tax preparation. The IRS would still need to have agents to examine returns, perform audits, and do other tasks.
Just because we have a stupidity virus sweeping the country from the Tea Partiers doesn’t mean that it’s Ok to make sweeping proposals based on a total lack of knowledge of the tax code and business practices.