One of the things that really bothered me about the erasure of Nettles as a character from Season 2 of House of the Dragon is the fact that it murdered one of the best possible plot points they could have done.
[Warning: Fire & Blood book spoilers]
I always really liked the idea that Rhaenyra's eventual hostility towards Nettles is motivated by the discovery that Nettles has no actual blood ties to Valyria; she's just a regular-degular commoner who bonded with a dragon by stumbling her way into a crude form of blood magic with all those sheep she'd been feeding Sheepstealer.
This revelation, that any random schlub can technically become a dragonrider and that it isn't something determined by Targaryen blood alone, would pose a massive threat to the concept of Targaryen supremacy. Their monopoly on these biological superweapons is the foundation upon which they justify and maintain their rule. Furthermore, Nettles' identity as a dragonrider not only poses a threat to the concept of Targaryen divine right, it poses a threat to the feudal system as a whole. You cannot have the peasantry finding out they can become gods among men, that everyone's places in life aren't predetermined by bloodlines and gods. It'll upend society.
So Rhaenyra is obviously anxious to be rid of this threat to her power, but her actions are misinterpreted through a lens of misogyny by the old septons and maesters who document history, dismissing it as "Oh Rhaenyra was fat and 30, she must've been jealous of the hot younger woman her husband obviously preferred, chicks be petty like that". That kind of misogyny has plagued Rhaenyra her entire life, it'd be ironic if the Westerosi scholar class inadvertently did a cover-up of this insanely devastating information because they just couldn't see past their own sexism.
All of this would be so fucking thematically on point for the ASOIAF universe, it would've been SO interesting...but then the showrunners replaced her with a pre-existing character from Valyrian dragonrider nobility.
It's indicative of a lack of foresight, understanding of the source material, imagination, etc. that doesn't bode well for the series. Such a bummer.