The characters in Persuasion are trying to adapt to a society in which class boundaries are more open than they used to be. In many cases, the characters who have done well in the old system cling tightly to the older, more rigid class structure. Others, however, are more open to judging people based on their individual personalities. The shifting social borders don't mean that class distinctions are disappearing, but rather show how the existing class system attempts to adapt to changing conditions.
The lower class characters in the novel are happier than the upper class ones, suggesting that a higher class status is an obstacle to happiness.
While money gives Captain Wentworth access to some upper class privileges, it is his appearance and manners that ultimately make him acceptable to the members of that class.