A better question - anyone left to dispute the fact that Civil War underperformed?
That's not a better question. That's derailing the thread. If you think it's such a great question make another topic for it.
On topic, Warner Bros. reactions, making changes to the directorial staff and decreasing the influence of Batman vs Superman's producer show how they felt about BvS's performance.
And nobody ever really questioned that Batman vs Superman had a good opening weekend. In terms of box office, the criticism is how quickly sales dropped. X-men's sales are really neither here nor there. They're disappointing on their own, but the movie was never really expected to perform near Batman v Superman at any rate. So really you have a strawman argument on top of a strawman argument.