Britain is not a highly taxed country

Whether we are taxed high or low, what is important is whether we get value for money, we being the public, not the bankers and CEOs of private companies.
I would argue that low taxation is not providing value for money: a broken NHS, broken schools, sewage dumped in our rivers, expensive education with a life-long debt, expensive energy, expensive food, etc.
This does assume that taxes pay for government spending, which MMT suggests it does not, although taxes do contribute to a fairer redistribution of wealth which may contribute to our well-being.