Is universal tax truly unrealistic?

Currently, our tax systems around the world always have many different types of taxations and some politicians have tried to simplify their taxation systems but all of their experiments ended in failure. I think that a universal tax could exist, but it requires a very complicated function to calculate the socially optimal taxation level for each individual in the society. This is one disadvantage of having a universal taxation system that it is almost impossible to come out one function that can consider all kinds of situations and factors and calculate the socially optimal tax for each individual. In addition, there are three time points that the government could tax one individual. The first time point is when one receives his/her incomes, the second is when one is owning his/her wealth and the final time point is when one spends his/her incomes on his/her consumption. Previously the politicians tried to impose a universal tax via the VAT channel. This channel is not effective that people's consuming habits are always changing over time. For example, in some western countries, people tend to consume more vegetables and fruits as they think this can make their diets healthier, meanwhile, in some countries, the price of meat is much higher than vegetables as in these countries meat is considered to be luxury goods. Taxing on people's wealth over time may not be a good idea, as this action could force people's wealth abroad. Therefore, I think that the only possibility of imposing a universal tax is to impose the universal tax on people's incomes. Then there are many factors that should be considered when we are forming the taxation function.

Overall, I think that imposing a universal tax is theoretically possible; however, in practice as there are too many factors that have to be considered and new issues can appear over time.