How many different ways do I need to explain it?

We already pay more than enough to cover everyone. Change the pipes the money flows through

First, we don't pay more than enough to cover everyone. About 10% of the population is uncovered today, and they need to be paid for.

Second, you can't just "change the pipes the money flows through" without dramatically changing who pays and who gets paid and what gets paid. You can't set up a system where everyone in the new system pays the same on day T as they did on day T-1 (much less having people get paid the same as they did the day before, or get the same level of coverage).

The distributional effects matter immensely, and they're deadly to the political prospects of these bills. That's why single-payer died in Vermont. The amount of tax they'd have to impose on workers and income earners was really high to cover the costs of the people who didn't work and didn't have much taxable income but still had health care costs. More importantly, payroll taxes and income taxes generally scale with income more than health insurance premiums scale with income (because they're percentages, and the latter are proportional). That meant that about 30-40% of workers would have been worse off under the new system than the old system. That was fatal to the plan.

If you mostly rely on a payroll tax, then a lot of workers end up paying more than they do today. All the new expenses (the uninsured, the underinsured, and the increase in Medicaid and possibly Medicare reimbursement rates) fall on them. There aren't enough savings to compensate.

If you impose a VAT, then retirees end up paying more than they do today. Because they're not currently paying a VAT.

If you have a transition period based on an age cutoff, the disruption gets worse - to the point where all your private plans explode. What do you think happens to employer group health plans in year 40 of Plan Steve, when the private coverage consists only of people over the age of 40 who have to pay premiums based on that actuarial cost, and there are absolutely no "young healthies" in the pool? Again, the distributional effects would be politically catastrophic.

Again, the distribution matters - and if you're not reducing costs by a lot, you can't set up a system that doesn't have a lot of net-losers. And if a big chunk of your electorate will be worse off in the new system than the current one, it won't pass.