My dad was on a Medicare Advantage plan offered by a traditional "insurer", and it seemed to be worthwhile - it covered some drugs better than OG Medicare, and had fixed copays rather than anything percentage based. Towards end of life (pre-hospice) they proactively sent a doctor out a few times for housecalls, with the goal of keeping him out of the hospital. And the baseline Medicare rules reigned in a lot of the usual "insurance" company shenanigans. If he had longer term health issues perhaps Medicare plus a Supplement plan would have made sense, but as it was it seemed to work out - had two years of paying the drug coverage gap (paying a few thousand dollars is essentially table stakes for health "care" in this country). I'm not a fan of "insurance" companies in general, rather just reporting my experience.

I kept his phone number (VOIP is like $1/mo), and I still get spam calls from scammers claiming to be "from Medicare" that "have a new card" for him - shamelessly pretending to be part of Medicare itself rather than a private company that's trying to steal his Medicare payments. Many times I'll ask them if their parents know they scam old people all day, or if they would want their parents getting scammed in their old age. Most of the time they just try to get me back to the script and think they'll convert me somehow ("I am not scammer").

I'm ambivalent on medicare advantage as a concept, but the scam companies are really what needs to be reigned in. Given that the benefits of medicare advantage is supposedly better coverage, I think a great way of doing reform would be to make it so people could change back to regular medicare at any time, and doing so would end up yanking back the premiums from the private company for the past year or two, unless they had actually paid them out for bona fide services. In addition to a lot more criminal enforcement against fraud, of course.