As a soon-to-be Canadian who has only experienced the US and Canadian systems, up here the quality of service isn't horrible and the waits for service tend to be shorter than they are in the US - but they are based on need rather than wealth. So someone in discomfort but no danger will end up waiting longer in Canada then if they were rich and lived in the US, but my relative with cancer was seen to promptly due to a high chance of complications if surgery had been delayed.
So I'm not sure what constitutes "most free healthcare systems" but Canada is apparently different from "most"
If you are rich and live in Canada, you can cross the border and pay out of pocket to receive treatment in the United States. I wouldn’t be surprised if Taiwan (the only other country with a Canada-style one-tier single-payer system) has a similar relationship with Singapore. Britain also has the ability to pay out of pocket for private practice care as an alternative to the NHS.
So I'm not sure what constitutes "most free healthcare systems" but Canada is apparently different from "most"