No one expects the shows to be exactly like the books, however when the changes made are far worse than the source material (like in The Witcher TV show), then of course people are going to complain. Also, there's a difference to changing the story compared to changing the fundamentals of the source material, such as significant changes to a beloved character so that they don't even resemble the character from the source material.I don't know why people expect a carbon copy adaptation when it comes to these TV shows. Writers have to have some artistic licence and can't just be copying the book exactly. Some books have far too many characters that just can't be explored in a tv adaptation and therefore some need to be scrapped. I also think if everything that happens in the book, happens in the show, then there aren't many surprises. Particularly with social media these days, book spoilers everywhere.
I think of The Walking Dead and the massive changes they made to that. Daryl was made up for the show and became a fan favourite. Carol died early on, yet lasted the entire series run. Those were just 2 changes that improved the show.
I love Henry, but if you're gonna complain about the writing, that is certainly going to put you offside. It would also be pretty annoying to have someone on set being a bit of a know it all about the source material.
The Walking Dead changed things and for a long-time they did a great job and therefore nobody cared, especially since 99% of the audience never read the comic. The Witcher had a good first season and then it has been a downward spiral since then, and again 90%+ of the audience are unfamiliar with the source material and they still don't like it. None of the changes made have improved the story nor the show.