Tax policy is also VERY complicated because there are a myriad of different economic situations, and the current aim is to achieve equity for all of them. This is most of the complexity in the tax code. Leave out all of those special rules (that try for equity) and the rest of the code is so simple you could teach an average 12 year old to write tax returns. Or just let the IRS calculate it for everyone and send them a report each year of the reasons for their tax bill.
Besides equity, the tax code favors people and companies that do things the government wants to encourage. For example, make home mortgage interest deductible to encourage home ownership. Or make companies invest in new equipment to improve our economy in general. We could review all of those things to see if they are all still things the government wants to encourage, I suppose. I bet nothing has changed though.
Republicans all want to make rich people richer, though very few economists think this will improve the economy. Almost all of them think that poor and working class people are much more likely to spend tax dollars you give them, and those dollars will circulate several times around the economy. This could also improve the wealth gap, which is getting very imbalanced. If nothing is done to improve that, you end up with a Third World pest hole where the rich need private armies to protect their families from kidnappers (or cannibals).
