Define "serious controversy".
If the fanbase being deeply split on it, along with hundreds of low reviews, a general fatigue for this characters, and the crew behind the movie defending themselves by calling the ones who disliked the movie who knows what then I don't know what it is.
Captain Marvel was by far the most controversial movie in the MCU, making very deep and violent waves in the water, most of them being for the worse. There are so many hundreds of reviewers on youtube that brought up facts that made the movie objectively worse in their eyes, while there still being people defending it for whatever reason. If splitting the fandom to such a level with your very first instalment isn't controversial, nothing is. They've literally hit almost every point.