The actress was 22.

And honestly, Incest was essential to the plot of Game of Thrones, it is the incident that lead to the whole thing. Bran, and so the audience, had to see who were fucking, so that Jaime can push Bran from the window. If I remember correctly, it was clothed sex at well. Realistic? I mean, some noble families had interbreeding, humanity is weird.

In HotD the plot revolvs around a family that marries their close family, traditionally. I think realism is a bad argument here, but it also isn't a moral failing on part of show writers.

Can 16 y old (character) consent to an adult man? I mean, not really. The show isnt endorsing it by showing it though, and the adult man is a shady character so it isn't a case of "but the good guy is doing it". The scene was pretty artfully shot, it focused more on what the character's were feeling than straight up porn.

There absolutely is unnecessary sexual assault and nudity in GoT. I think you chose poor examples of it.