Maybe a "Cadillac plan" is one that goes beyond the normal purpose of "insurance." In every other case, people buy insurance to cover unanticipated expenses that cannot be paid out of pocket without hardship. People don't buy "auto repair insurance" or "rent insurance" because both are anticipatable expenses. IMO, medical insurance should be the same thing: I know I'm going to get sick, wear out, maybe hammer my thumb: I should anticipate the normal medical expenses attendant with living. Other expenses are unusual: a liver transplant, brain surgery, etc and will exceed what is normally expected. When these medical costs exceed what is normaly expected, that is what medical insurance should be for, IMO. Plans that pay for regular anticipatable expenses might be termed "Cadillac plans."
Of course, no one knows what a "Cadillac plan" means to a Texan. He might be talking about medical insurance plans with horns attached to the hood.