Modern family life is lived against the background of cataclysmic cultural and social change - changes which have prioritized the individual self over the social group and have inevitably re-sorted family relationships - royal family relationships no less than others. In The Crown's telling, this conflict goes back, like so much else, at least to the 1936 abdication crisis - a calamity that has ever since hung over Elizabeth and her family and still very much does in season 4. The ambiguous way the infamous Duke of Windsor was treated in the earlier seasons - alternately seen as a terrible culprit, disloyal to both family and country, alternately seen as a sympathetic figure, drastically penalized for daring to prioritize his personal happiness - highlights this tension. Repeated in part in the story of Princess Margaret, this tension now comes to a head in the Diana drama.
Unlike Margaret Thatcher, Lady Diana Spencer, daughter of an earl, country-bred, neighbor of one of the royal family's homes, easily passed the Balmoral "Test." On the one hand, there was Charles, under extreme pressure to settle down at last and to do his royal duty,. On the other, there was Diana, probably too young for the role and certainly too young for Charles (whom Anne infelicitously characterizes as older than his age). Obviously entranced by the romance of the fairly tale Prince Charming. Diana was on paper a perfect choice for the role of Princess of Wales and future Queen. In fact however she was at best unprepared and at worst temperamentally unsuited for the role she was about to assume. In The Crown, it is Margaret and later Anne (two survivors of failed marriages) who are willing to speak the truth that the great 20th-century fairytale was a catastrophic mismatch.
It is also Margaret who uncovers another scandal lurking in the shadows of the family (in this case her mother's family, not the Windsors). This terrible and unnecessary instance of familial cruelty helps tip the scale in souring the audience on how family makes impositions upon people's lives. On the other hand, as the Queen reminds her children - and especially Charles - they are actually far too privileged to complain so much about the expectations imposed on them. Ultimately it all comes down to whether or not seeking to have a happy marriage is to be thought of as some sort of universal right (as Edward VIII had implied in 1936).
Temperamentally unsuited to her role (too young for her age as Anne suggests), Diana also epitomizes the contemporary mistake of equating celebrity with significance. Charles, in the other hand, in addition to his primary fault in never having given up Camilla, seems completely incapable of appreciating what Diana does contribute. Whether Diana deserves primary credit, for example, for keeping Australia a monarchy, as the show suggests, may be debatable; but there can be no question that her celebrity and star power did enhance the institution and might, if better appreciated, have been an asset rather than the liability they became.
Of course, the audience cannot be unaware of the rest of the story. The historical fact is that the Prince of Wales is now at last happily married to Camilla. What once seemed unsuitable has proved very suitable indeed, whereas what once seemed the ideal solution proved to be a nightmare for all involved. So what does that say about duty and about the renunciations imposed on individuals for the sake of the family? That primordial question, so starkly raised by the abdication crisis, continues to haunt, with no prospect of resolution.
One is reminded of Harold Wilson in season 3 telling the Queen that people don't really know what they want the Queen and her family to be, because they want multiple contradictory things simultaneously. The series dramatizes the universal fact that the same may be true of contemporary family, that the benefits of adhering to traditional family expectations are still very much desired, but so are the comparably attractive benefits of leaving those expectations behind.