That is the first time that I have seen a reference to something that happened at times over 500 years ago as 'newer'...
Take an anthropology or archaeology class - then anything less than 1000 years old is definitely new.
As to whether or not marrying commoners is new in the BRF (in terms of contemporary versus not), while precious monarchs have of course married women without princely titles, most did marry women who were the daughters of people who held titles. Until William, the only notable member of the historic BRF that I can think of having married someone not related to or descended from anyone with title is John of Gaunt, who of course married his mistress.
King John's first wife was a Countess and the daughter of an Earl. Her paternal grandfather was an illegitimate son of Henry I.
Elizabeth Woodville's maternal grandfather was the Count of St. Pol, Conversano, and Brienne. Her father was pretty self-made, but he was eventually granted an Earldom.
Richard III married the daughter of a Countess (in her own right). Her father, who became an Earl through his marriage, was the son of another Earl.
Henry VIII married in order a Spanish princess, the daughter of an Earl (and the granddaughter of a Duke), the daughter of a member of the gentry (I'll agree to call her a commoner), the daughter of the Duke of Cleves, the granddaughter of a Duke (through a younger son), and another daughter of a member of the gentry (her grandfather was a Baron). So, really 2 out of 6 were not of the aristocracy, and even then I'd question how not aristocratic they were.
Jane married the son of a Duke.
Mary, Queen of Scots married the son of a king then two sons of Earls - while I would agree that she definitely took several steps downwards, I wouldn't say that Henry Stuart or James Hepburn weren't of the aristocracy. Henry Stuart was his father's heir apparent until his death, and James Hepburn inherited his father's title.
James II married first the daughter of an Earl.
Pretty much none of these royal consorts were without aristocratic or royal pedigree, something which Catherine cannot claim. Sure, if this was 500 years ago (or even more recently) her family most likely would have been of the gentry owing to their economic class, but they aren't, and that does set her apart - the closest equal she has is Katherine Swynford.