1. Some people just don't like adaptations, and they need to understand what different mediums limit in terms of story telling. If you think of WoT as being 10,000 pages of content, and how you would shorten that to make it finish-able within a single human lifetime, then they have to change some things. But I gotta say, I think they capture a lot of the good of the books within the show.
2. Most people just have a picture in their head of what the thing is going to look like, and when that picture doesn't match up to what's made they're unhappy. And they don't understand why they couldn't just do the thing in their head because they don't understand the limitations of the medium.
2a. I think a thing that's important to a lot of people is the characters looking like the characters they imagine, and when casting is more diverse than that, people have a pretty negative reaction to the characters not "looking" like the characters. I think this ends up being more true the further from the description people feel like the characters are. ^This is a thing that has been hurting LoTR for a lot of people, in my opinion. I don't think it's a reasonable thing to expect.