Frugality was not their métier.
Unfortunately, the last couple certainly were lacking in political savvy.
Marie-Antoinette was not cut out to be a queen and neither was her husband. They are both examples of what happens when the hereditary monarch is not suited to rule.
Louis wasn't that dumb but he was very timid and shy, more interested in hunting and making clocks than governing. Marie was married at 14 to a husband who could not consummate the marriage for 7 years (possibly a too tight foreskin).
Interesting page here about his possible phimosis: http://www.historyofcircumcision.net/index.php?option=content&task=view&id=78
She wasn't very smart about politics. It too years for her to have a child (which the French blamed her for). The French journalists totally trashed her reputation, accusing her of everything from being a lesbian to having an incestuous relationship with her own son (8 years old at the time).
Neither of them was capable of handling France's financial problems, partially caused by a huge debt incurred through their support of the American revolution. BTW, we never paid them back.