I don’t know the tax system in the UK. None of us does, I venture to say. perhaps you can enlighten us.
In this country it is absurd, it is unjust, it is corrupt, and for that last reason it is impossible to reform - political careers depend on it remaining what it is - absurd, unjust, corrupt. We’ve been talking about the reform for at least 30 years - no can do.
That is why tax evasion (by those who owe taxes, not by the moochers who collect from the gummint!) is considered by many a noble occupation in this country.
I can understand your frustration. Politics and money are very closely intertwined in the US and that has led to a tortous tax system with innumerable exceptions and add-ons, all no doubt made in the name of "fairness", but which in fact are nothing more than stroking some politicians political base. As you say, it is incredibly difficult to reform such a system, and that leads to people "playing" it, or at least cheering on those who do, as evidenced by some of the comments on this thread. I get the impression that the system encourages people to cheat, much like prohibition made millions of perfectly ordinary americans into criminals. It's not good, but as you say, it's going to be a brave politician who tries to reform it because of all the interest groups that will be threatened.