Please understand what "out of pocket maximum" actually means. It only applies to "covered" procedures.
If that experimental surgery isn't covered your OOP maximum doesn't apply.
Also please understand that insurance companies like to consider thirty year old tests/procedures/treatments as experimental/unproven and will consistently use that as an excuse to deny coverage and not apply them to your OOP maximum.
Hope you can afford an attorney if that happens.
Will this likely happen to you? Not at all. Can it happen to you? Absolutely.
All of these things apply to group insurance, as well.
Pre-ACA many plans didn't have an out-of-pocket maximum even for covered stuff, and most had lifetime limits on coverage as well.
That said I would strongly recommend everyone who goes independent look into long term disability insurance while they're healthy. Freelancers Union has a decent group policy available to anyone for pretty good rates.