The citizen can either pay that number, or offer amendments to the details which imply a lower rate (or higher if you're a masochist, I suppose).
That's independent of the complexity of how that number is derived, and in balance I would rather the US (as a citizen thereof) use this sort of system than the one we happen to have.
There is nothing inherently wrong with that. Whether you do or do not agree is a different question.
It's interesting to look at different cultures:
The Swedish word for "tax" is "skatt", which literally means "treasure". Historically it was part of the treasure to be collected by the monarch and other people in power. So, not really a way to cover government expenses, but for somebody in power to enrich themselves further. Luckily, the country has moved on from that, just kept the word (and the king).
The German word for "tax" is "steuer", which literally means "to steer". That makes it clear that those fees are not just collected to finance government expenses but to even steer society in a certain direction, i.e., what you mean with policy.
Tax credits for education, clean energy, penalties, small businesses, mortage interest, each one of those one-off changes adds complexity, and in total ultimately can make the process dramatically more difficult.