This sort of crap is part of why so many people are scared of the idea of a national healthcare plan. You would think Medicare would be easy, medical coverage for people over 65 or the disabled, paid for by the taxes you (and others) are paying your whole lives, simple and done. Except it isn't easy at all. Only Part A (hospitalization) is covered by the taxes. And it only only pays 80% of costs, with no annual out of pocket max (remember how having that was a huge selling point for ACA plans?). Oh and there's also a PER INCIDENT deductible for each in-patient hospitalization. And you better hope you don't need a visit longer than 60 days in the hospital, or 20 days in a skilled nursing facility or you're going to start paying for that too.
Then if you want to, oh I don't know, see a doctor so you don't go to the hospital in the first place, that's Part B, but now you're paying a premium, and also have a new deductible (thankfully only once per year for this one). Still only covers 80% of the costs, still has no out of pocket max. And all that "in network / out of network" crap you have to deal with in private insurance? Yeah that's still a thing, they just call it "participating" and "opt out" providers. Only unlike a lot of private plans where at least there's some (crappy) out of network coverage, if you see an "opt out" provider, medicare won't pay at all, no matter if you submit the claim yourself or if the service was a medicare approved service. So that's nice. Oh and if you don't sign up for part B
What's that you say? You'd like to be able to take life saving medications and prescriptions that could also keep you out of the hospital? Why that's yet ANOTHER plan (Part D) you need to sign up for, with yet another premium (medicare currently claims between $4 and $150 monthly in my state). And then like always, drugs tiers with co-pays and then the infamous "donut hole" (I worked IT for a pharmacy, the number of their patients who just... stopped being patients when they hit that donut hole every year was disturbing).
Don't worry though, Medigap is here, an insurance policy you can buy to pay for the stuff your national insurance that you're already buying doesn't pay for. For a mere $200 - >$1000 / month, some or all of those deductibles listed above can be covered.
Oh and did we mention that if you fail to sign up for part B or part D within 60 days of being eligible you might have to pay an additional penalty on your premiums for life? And as you pointed out, you might never be eligible for medigap if you don't get it the first time around. And none of that includes vision or dental coverage.
So how much does it cost to be covered by medicare? Well with all the plans and a medigap plan as well, anywhere from $200 - $2000 / person / month just in premiums. Yeah ...