I think I know why there are so many negative reviews, and I would say it's because its a finale movie. It's the final one to the franchise so it doesn't do the new exciting things people want it to do but at least contrary to Game of Thrones, it doesn't ruin all of the characters and provides a believable ending to the story.
I enjoyed it, I thought there was some funny parts that I actually laughed out loud to which is rare. The fight and chase scenes are so well choreographed and dynamic. The only slightly disappointing one was the fight scene with the Chameleon. You didn't feel the same kind of awe and fear that you felt with Tai Lung or Lord Shen. And the ending with all of the past kung fu fighters watching did feel like a bit of fan service (i.e. kind of awkward). But not bad! Doesn't deserve a one star and at the very least, they had the furious five for like one minute in the credit scene lol.