I retired early and went on ACA plans for 10 years. Those plans are similar to how Medicare Advantage plans operate: with defined networks. And the rules about who you can treat you "in-network" and where you can go "in-network" can change at any point. In most businesses, if you "change the deal" the customer can walk, get their money back, and find another provider. But not in the case of health insurance.
I started the first year the PPACA plans went active, and I watched over the years how the insurance companies kept changing the rules. I get it. They needed to save money to compete. But I got fed-up with that process and want to avoid anything like it, if I can. And I can, by avoiding Medicare Advantage.
Here's one example... I traveled to another state to see a world-class doctor and it was covered. A few months later, but the next year, with "the same insurance" they denied the claim. They pointed me to an 80 page PDF and expected me to notice that a paragraph had been REMOVED from the document year to year! Oh, and, by the way, that document was not available to me until AFTER I purchased the insurance on healthcare.gov! I fought that and won.
Another example I ran into is "stacked deductible", which got outlawed, but I got hit with. This where if you get two individual policies for husband and wife, the insurance kicks in at, say $5K, but if you buy the exact same coverage with both of you on one policy, the insurance doesn't kick in until $10K. I fought that and lost. And later they outlawed the practice, so the judge in my case was wrong...probably didn't want to get appealed.
The insurance company would see where they were spending "too much" and set it up next year so it was harder or impossible for customers to consume resources in a certain way. Insurance companies see their customers as ants to honey...they spray "Raid" on the biggest trails.
Besides those reasons, as a matter of principle, I don't buy things that involve a "hard sell."