Well, one of the problems is that since 50% of the people do not pay income tax, most of them really do not care that much about the tax code.... they just want to file and get their money...
What makes you so sure of that? It is the tax code, even just a few pages of it, which enable many of those people to pay no income taxes. Some of them receive refundable credits but many others (such as my dad and many other elderly people) simply have zero tax liability so they pay zero taxes and receive no refunds.
The code is for the other 50% of the people and for a good majority of them it is becoming combersome.....
But for many of them, such as those who use one of the short forms, the tax code is hardly cumbersome. And even for those who file the long form because they are barely unable to qualify to use a short form (or who file a long form unnecessarily), the tax code is hardly cumbersome. Even for someone like me who has filed the long form every year since 1989, most of the lines on the 1040 form are left blank. Most of Sched A is pretty easy, too, just copy a few numbers from the 1098s or from the state tax return.
Remember back when after you determined your taxable income it was real easy to figure out how much you owed
You just looked it up in the table and put it on the form.... now, you have to do a lot more calculations.... and then you have to see if AMT kicks in.... and I might be wrong, but don't you also have to figure out if you can deduct all your deductions
Actually, what you are describing is what I do for my state, not federal income tax form. The state, rightly or wrongly, fairly or unfairly, taxes all income alike, so that special cap gains and QD worksheet does not exist. If the feds taxed all income alike, it would simplify things quite a bit, making it like my state's calculation (i.e. look it up on a table). If you don't have any taxable LTCG or QD, then the worksheet does not apply.
The other two things you mentioned (itemized deduction limitation and AMT) are only for higher-income earners. In all my 27 years of filing income tax returns, I had those things apply to me exactly ONE time, in 2008 when I had that big company stock payout.
Otherwise, one's taxes for many people are pretty much this: "A W-2 for wages and taxes withheld, maybe a 1099 for interest, a standard deduction and personal exemption, look up tax on a table, compare it to taxes withheld, and see if you get a refund or need to write a check."