Um, Mal... it's a shitty sequel. If it was a damn good movie in its own right, then people wouldn't even be dissing it aside from saying, "Well, it has little to do with The Dark Tower."
Plus, if you're going to market it as "The Dark Tower," then suddenly you want to have your cake and eat it too. Calling it a "sequel" is actually a sloppy lie. What King allowed at the end of his tale is a "retelling," not a "sequel." So while the same GENERAL story would unfold again, it would give the filmmakers a chance to do their own riff on the material, change things that couldn't be filmed, and so on. a "sequel" doesn't mean "reduce a 2000 page story to 95 minutes by not doing anything from the book, changing the few characters that remained, and toss in a few random baubles out of context as lip service."
Maybe they should have just done all new characters, as part of their "sequel," to avoid confusion.
Ironically, I have a friend here at work who was bitching about all the negative RT reviews, "let people make up their own mind," and ranting at the reviewers. then he saw the movie. Now he complained more about the movie than I did and how terrible it was. We did both agree Idris Elba was decent as Roland, if he had had a better movie to be a part of.