The people to blame for complicated taxes are Congress and the President. Over time Congress slips in all sorts of special taxes and special exclusions to support their interest groups. The last time there was a concerted effort to simplify the tax code was 1986 https://en.wikipedia.org/wiki/Tax_Reform_Act_of_1986 .

Critics of the 1986 Tax Reform Act said, why bother simplifying the tax code when Congress will just make it complicated again? The response was sure, we'll just need to clean up the tax code again every 20 years or so. Well that's never happened since.

In 2017 many in Congress wanted to simplify the tax code. Unfortunately Trump said he didn't want to simplify taxes, he just wanted to lower them. As one great example, some folks wanted to eliminate the State and Local Tax deduction (SALT), which is a complicated deduction. (Example: You file federally based on "estimated" state and local taxes, but if you get a refund or owe state and local taxes, the next year you have "adjust" your prior year's deduction.) Instead of eliminating them, the 2017 tax bill just phased them out at higher income levels, which just adds complexity to an already complex part of the tax code.

Certainly the act of filing one's taxes can be made a bit simpler, but it seems there's never any incentive behind actually simplifying the tax code itself, because every tiny change to the tax code creates winners and losers who object.

There's a lot of good arguments that Simplicity shouldn't be the most important aspect of a tax code.

Complexity is a good thing if it allows people and businesses to do the things you want them to do and they want to do.