A fair comment. I'm guilty of not developing my thoughts clearly enough and I thank you for pointing it out.
The sex in GoT is over the top in my view. Your second paragraph is a pretty close summation of my actual thought on this so I will let it stand with my thanks.
Just look at DC these days. Tell me there aren't power struggles of a similar nature behind the scenes, just without the overt bloodshed.
I believe there are. However, the question is not whether political violence, betrayal, murder, and sordid sex exist. We all believe they do.
The issue raised by your original post is whether fiction that focuses solely on those elements is more "adult" than fiction which does not wallow in such things. LOTR doesn't avoid pain, death, betrayal, and other evil, but situates those elements in a fictional milieu in which beauty, love, selfless friendship, and sacrificial heroism are ultimately "more true."
There are different ways to view these things, but personally, I think of people who mistreat others, who seek power without accountability, who aren't trustworthy, as fundamentally immature, adolescent. Love and sacrifice are the grown-up things.