If a base rate that the society agrees on is e.g. n %, then, in my opinion, everyone should pay that n %. But in reality the poor people pay n % because they have no time to even think about optimizing it. As they often work around the clock to make ends meet. While the richer people hire professionals to take care of their taxes and optimize them to the extent that they pay significantly less than n %. And then there are super rich, some of whom, such as Donald Trump, pay almost no taxes at all.
This is, in my opinion, wrong and significantly contributes to wealth inequality. And therefore I believe that it needs fixing.