Let us not forget that some of these most democratic countries in the world still or until recently still had a royal couple with "oldfashioned" partners...
And what changed when Sophie and Georg married? Nothing!! And, perhaps, Georg and Sophie love each other, as nothing else is important, as nothing will change. I do hope they do. And Guillaume and Stephanie love each other, you can see that and she is not his "equal" by Russian standards. She is bright, educated and a delight. If all the rules applied she would be out. And Prince Aimone marriage did what? Did he get a throne and, too perhaps he loves this woman, which is great. And among Monarchists, who cares.. They have to live their lives, not hope for some bright tomorrow, that, most probably, doesn't exist.
And yes, you point out the great marriage between Juan Carlos and Sophia, a real model. Poor Sophia. Or Albert and Paola, another virtuous example. They, to their credit after years of travail, put things together. And Elizabeth and Philip, hidden stories from those who know how to conceal their peccadillos, before the rabid press started their invasion. So,look at all the very nice Constitutional Monarchies, all have what you would call "commoner" spouses and they do very nicely. Maxima, Matlilde, Mary, Mette-Marit, Leteiza, Daniel, Kate and of course, the mistress, Camilla. And by the way Henri of Luxembourg married a Cuban of hardly distinguished parentage, by your standards or his mother's. But Maria Theresa is great. I never called these Constitutional Monarchies fossils. They are4 smart and have kept in step with the times and they have "real thrones". But the Russian pretenders are fossills. They want what has long passed by. 100 years ago, soon. Georgi is young, now. He deserves the best he can find and have happiness for himself. Not for outdated Monarchists standards, by a regime that was removed almost 100 years ago.