Your post remains me of how Russians often react on their forums to posts regarding the corruption in Russia. There are undeniable proofs of how corrupted Putin regime is. All ministers, members of president administration, local administration, judges, generals, etc. end up owning multi-million properties both in Russia and Europe/USA, but many regular people find the stupidest excuses of how the system is fair and just, but "the doctors office does not code the claim correctly".
Check out the insurance companies profits. Those are directly linked to denied customer claims. Claims are not denied en-mass, by accident obviously - unless you're a complete fool.
Oh and by the way: health insurance company profits are essentially capped by the government via medical loss ratios. They don’t make more money the more they deny otherwise they will be forced to send rebate checks (like what happened during Covid)
And they do use denial and remark codes to indicate the services don’t justify the diagnosis.