Constitutionally, it's significant that senior members of the Royal Family are marrying individuals who don't trace their ancestry back to members of the aristocracy. Historically, this is a significant departure from tradition and may or may not indicate a correlation between evolutions in society and evolutions within the institution of the British Royal Family. The trend, I think, is about fifty years old.
Diana Spencer was an aristocrat by birth, but Prince Edward's wife Sophie was not. Andrew's wife Sarah Ferguson did have aristocratic antecedents, going back generations, I think. I don't think Princess Anne's first husband, Mark Phillips, did.
Interestingly, I think that on her father's side, Kate Middleton had some gentry antecedents - but not aristocratic. If you go back far enough, lots of people have 'blue blood'. Doesn't Danny Dyer, the Eastenders actor, have royal blood to about four English kings?
I don't agree with the Press reporting on a person's social antecedents or ethnic ones, at all. Especially not now. We know that the Royal Family and aristocracy don't only marry other aristocrats, as they did 100 years ago. Unless the press are going to make clear why they are doing it: to show the way the Royal Family is 'modernising' their structure, if that is what the journalist thinks is happening, then don't say it because it it isn't following the principle that everybody in British Society has an equal right to try for any job or position, regardless of social/ ethnic background, and as long as they are qualified.
I can see the press might want to write about constitutional and historic change, but the cack-handed way they are going to do it to make it snappy, will only obscure their meaning and leave readers thinking that they are being personally unkind to the person marrying in. I'm not convinced that most people care about historic constitutional evolutions, so I think they can cross it off the list of key angles every newspaper article should contain when written about a royal marriage. Time, date, guests, BBC or ITV, is sufficient.