I hear you and it's no fun at all...(please reach out if I can ever help...)
The conditions that are the biggies that pose problems for a supplement are: COPD, diabetes insulin, congestive heart failure, parkinson's, dementia...if surgery is recommended and haven't done...or hospitalized/needing facility care.
So to be honest - you have to be very sick.
Another thing to remember is that if you have always been on a Medicare advantage plan and never were on original medicare A+B, you are entitled to your special enrollment (no underwriting) if you want to go back to Medicare and a supplement....
I was curious the other day what the Medicare part B premium was from over 15 years ago when I worked with retirees and sold insurance...so I can't say I know what the premiums of supplements are but I would randomly guess $150-250...
And companies want you guys to switch and make it feel like each year you have to consider what's out there...but Medicare Advantages plans are really so very very similar. You don't have to do anything and you get re-enrolled in what you already have...so don't let anyone get you worried that if you don't "do something" you lose coverage.
Keep well! Have an awesome day!!!