I don't understand what is going on - nothing unusual about that.
UK public expenditure has increased as a % of GDP to the highest levels since the 1980s - bar covid and the 2008-10 financial crisis. The fall in public service quality is not obviously due to low taxation and cuts - perhaps budgets have not increased sufficiently.
- have public expectations changed which means that a return to earlier low levels of taxation is unachievable, and that taxes should be even higher
- is there some massive fraud or corruption syphoning off tax revenues to offshore accounts
- is the money spent on public services being poorly directed, managed or wasted
The first bullet is a real possibility - but honesty in fiscal policy seems subordinate to political expediency and electoral ambition for both major parties.
The second is the stuff of conspiracy theorists - but to my mind needs quantification and evidence to be plausible.
The final bullet may be a substantial contributor to problems. Too much legislation adding to cost, delay and inefficiency often the product of vocal minority groups. Overcentralisation making local democracy close to ineffectual. Attachment to obviously failing projects and policies.
A society in which all feel empowered and content with their lot is a worthy goal but there is a price to be paid.
Were the UK a person it would be past middle age, comfortable, risk averse, contentedly growing older and weaker. Change is disruptive and difficult but if we want "better" we need to accept it.