I'm told (by a high school friend who turned 65 this past August) the approach, on top of the automatic plans A and B, is to pay for a prescription plan, and if there's an affordable plan G, to get that. (This is all word salad, or some kind of salad, right now.)
MediCare A and B are standard. They cover some, but not the most. of what you may need, like hospital stays, prescriptions, minor/major surgeries.
United Healthcare has medical plans for all kinds of needs. When I retired and moved out of California, I forfeited my comprehensive Kaiser medical plan, BUT, my retirement included a monthly allowance to purchase insurance. United Healthcare Plan F is what I have, but I understand "F" is no longer available to newcomers. In many cases, my needs are covered 100% as long as they are short-term or one-time.
When you talk to someone about Medicare, get the facts on what is covered and what isn't. Either go with an additional medical insurer or, at the least, inquire about Medicare Part C. An additional insurer is better for you in your "decllining" years.