Basically, title. On my side, it might be unpopular, but I was quite disappointed with the Mistborn Trilogy. The world is interesting, I like the concepts, but I could just not connect with the characters? I finished the first book and started the second but could not finish it.
Way of Kings is incomparable. A shining achievement. Unfortunately each following book in the series gets worse, until the last one is just an overly long exposè on mental health problems.
I didn't realize how harsh my review sounded until re-reading it just now. I enjoyed the books too. Because the first one was so amazing, the rest were still good even though I felt like they got progressively worse with each book. I was pretty frustrated by the last one, and I was ready for it to end long before it did, but it was still entertaining. The series is a big achievement, it just needs tighter editing like you said, and I didn't enjoy the mental health exposè. I don't read fantasy to get messages about real world problems, I read fantasy to escape from the real world. All that said, I still strongly recommend WoK to people, I just let them decide on their own if they want to read any of the sequels.
Holy shit yes. I thought Way of Kings was incredible, and thought I found my favorite book series. Then the next book was fine, and the third book was so insufferable I quit after 800 pages. Never even made it to book four, which I hear is even worse.
Try some of the other series by Sanderson, it was his first series, and not the best written. If you don't like his other work too, then maybe he just isn't for you.