It seems like countries will do anything but tax carbon.

Carbon is not the only concern here, it is also excessive water use, excessive land use, higher logistics pressure on ports and such which can be reduced if these are made to a higher quality and a reduced quantity.

https://taxfoundation.org/data/all/eu/carbon-taxes-europe-20...

For the same reason tax codes are complex. If you have a simple law, there's no way for a politician to say to a group of people: "If you vote for me, I will get you a special favour".