I started reading Martin in the 70s when he was publishing brilliant short stories like "With Morning Comes Mistfall" and the truly haunting novel "The Dying of the Light", which had about as original a setting and premise as I've ever read. I read damn near everything he published from his beginnings up through GOT.
I read GOT when it was first published and was...underwhelmed. But by then I was tired of "Epic Fantasy", especially the neverending series that had become the default setting for maximum extraction of money.
In fact, I've come to really tire of sequelitis in books and movies. Either the protagonist is functionally immortal and thus there are no stakes, or/and the author is lazy/repetitive/unoriginal.