I have an HSA, but I'm painfully aware of how it's just another boondoggle for the wealthy. I can dump cash into it on top of the limits for my 401k and IRAs, and pull it out tax-free with no limits once I turn 65.
Another good example of how an idea that sounds fairly good on paper turns out to be another benefit for the rich in real life.
The real trick is to save medical receipts for years/decades and reimburse only when you actually need the money, paying out of pocket until then.
Does that trick actually work?
There is no time-boxing on reimbursement, so it should. HSAs are only about a decade old, so no one has done the extreme versions of it yet, but a decent number of folks are squirreling away receipts and letting the money grow.
Kinda like a backdoor Roth, no rules prevent it, so it works.
FSAs (other than LPFSAs) cannot be used with HDHPs, which are the plans that allow HSAs.
An actual HSA is your money. If you don't spend it on medical care, you can withdraw it when you are elderly as normal money.