UK here too and agree with the everything but the national insurance part is a common misconception. The amount you pay in national insurance has no direct tie to benefits or the nhs, and has not been connected for a long time.

All national taxes go into a big pot which the government allocates any way it wants in the budget. For example, the recent class 1 employers national insurance rate increase from 13.8% to 15% does not mean that increase in funding goes directly to the NHS.

The amount of years that you paid national insurance for in your life does effect the amount of pension you received. Once you’ve worked x number of years, you receive the full pension available. The amount you paid has no impact. In fact, you just have to have been paid a salary of the lower threshold, which means technically you don’t pay any national insurance, for that year to be marked as qualifying. Lots of owner managed business pay themselves salary of the lower threshold (£6.5k), then pay the rest in dividends - results in them meeting the pension eligibility for that year, pays no national insurance, pays no income tax, and then pays the lower income tax rate for dividends.

Fun fact, once you hit the legal retirement age, you stop paying national insurance even if you carry on working. This makes it a regressive tax!

Successive governments have not made this clear because it is politically easier to raise national insurance rates (“helping the NHS”) than income taxes, even though income tax is a more progressive tax and it all goes to the same pot.