I don't know what your experience is with medicine here and medicine abroad but that statement is the complete opposite of my experience and the experiences of my family members. And I'm one of the lucky ones - I'm English but have dual American citizenship. So I have NHS when we go back and am also covered by our BCBS PPO plan.
I was diagnosed with a rare disease 15 years ago that's seen me land in more doctors' offices than I care to remember, both here and abroad. The pathway to seeing a specialist here is simpler and so much faster than seeing a specialist in the UK.
I would chalk it up to me having good luck here and bad luck there, but my family (who all still live in the UK) have worse stories about long wait times, convoluted processes, and inferior medical care. My BIL died under the knife during an outpatient surgery in London.
You can talk about the role insurance plays here but when it comes to actual care there's no better place in the world to be sick.