[1] "works" is an interesting point because it isn't clearly defined, and usually means different things to different people.

Ever experience of the system is "unique" - there is this mix of human patient with human provider with finite resources with medical knowledge with time. So there are plenty of examples of long waits, bad service, unfavorable outcomes, even death. It's not hard to cherry pick bad experiences here.

No health system will make everyone live forever. Death comes to us all sooner or late. But universal healthcare works in many places in raising the overall standard of public health, without bankrupting people in the process.

Given that its always spending limited money, and only scales at human rates, its far from perfect. But, at least for some, its better than a "health care level based on your wealth" system.