I mean I agree it's been made pointlessly complicated. But this is all born out of the fact that everything we do in the US we insist on finding silly ways to insert unnecessary private middle men. But the fixes people are calling for with national healthcare policies like Medicare For All are precisely to do away with the problems you bring up AND extend the resulting system to everyone. I think a good start is just doing away with the things you bring up even if it's just for 65+ at least.

FWIW I am on Medicare (due to disability) and I expletive love the experience compared to the gold plated, Silicon Valley tech company, private insurance I had before I became eligible. I've not had to think about a prior-auth or appeal in the entire time. I've had no reduction in the doctors I can see (I saw specialists across the country). And I receive about $8,000 of specialty drugs a month without any questions.