I hated the ending of Game of Thrones but I thought the show had been poor for a while so it didn't bother me that much in the grand scheme of things. The petition was just ridiculous entitlement. Fandom has far too much access to creators these days (and creators are far too willing to engage with whoever shouts the loudest). A big part of fandom and fanfiction is to take those endings you don't like and do something different with them, and as you say, writers are never going to please everyone so why bother trying?