The problem is people duped into switching into Medicare Advantage, which they can’t undo. See https://www.newsweek.com/how-medicare-advantage-scams-senior...
https://www.medicare.gov/sign-up-change-plans/joining-a-heal...
>Medicare Advantage Open Enrollment Period. From January 1 – March 31 each year, if you’re enrolled in a Medicare Advantage Plan, you can switch to a different Medicare Advantage Plan or switch to Original Medicare (and join a separate Medicare drug plan) once during this time. Note: You can only switch plans once during this period.
But you are only guaranteed to be able to join Medigap during your initial enrollment at 65. If you switch back from Medicare Advantage to Original Medicare you are not guaranteed to be able to get Medigap. This can leave you stuck. It will possibly vary from state to state so it pays to get up to speed with the rules in your local state.
If you're expecting to be sick in old age or if you get Medicare due to a disability that is likely to have a lot of expensive treatment or require you to see different doctors in different areas it is best (IM-somewhat-experienced-O) to take Original Medicare.
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 ...
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.