I haven't really seen this "dislike" you're implying, but I agree that there's a degree of apathy towards him. People tend to feel more strongly towards Garrosh, Vol'Jin, and Sylvanas, for better or worse, and tend to be more neutral towards Baine. It doesn't mean he's a bad or even a disliked character, he just lacks the visibility and impact of some of the other Horde leaders, especially for players who have not read the books.