This masterful book employs many amazing writing techniques and creates a powerful and moving story.
First, it doesn't try to sugarcoat the inherent racism, which is so important, especially at the time it was written. Harper Lee, who was from the deep south, created a novel that is entirely against racism. It presents everything it was, and it appeals to us because it is so real. I understand the complaints about the language, but in reality, that doesn't detract from the story but adds to the image and the setting.
Second, its writing techniques are considered some of the best of all time. Using an unreliable narrator, especially someone as young as Scout, adds to the greatness of the book. Especially as we watch her character grow from the irresponsible child that would attack anyone, to the much more mature girl we see at the end of the novel.
Thirdly, I don't understand the idea that this book is sexist. It is again simply saying how it was. Harper lee is possibly the most accomplished female author of all time.
Finally, the pacing of the book is created such that it doesn't follow the natural hero's journey that we've come to know and love. I do understand that those who may lack the intelligence or attention span to enjoy it may find it winding and rude, but the deviation individualized the book.
Overall, this book is amazing, and possibly one of the best novels of all time.