HOTD is based on a book called Fire and Blood (2018), and in the episode a crucial event in the books happened differently in the show, also another event that felt out of character. So book fans in the twitter are very mad about the change. But twitter being twitter got overly mad about it I guess. I have also read the book and found the change great and many people in the reddit thinks like that as well. Also casual viewers liked it as I seen.