DOFP is the highest rated film of the franchise, and the timeline and continuity was all over the place. It doesn't even explain why Xavier is still alive, why wolverine has metal claws again, why Kitty Pryde can send people back in time, and why Trask is a short white dude in the 70's.
Yet DOFP was reviewed on it's own merits. What critics care about is the quality of a movie.
Well, that's true in many ways as far as critical reaction goes. But I think DoFP created a very good distraction from those things with its time-travel plot and Sentinels (both new to the franchise, at the time of X2 the idea of Sentinels was axed as too way out!!!!). Also, the addition of many of the Original Trilogy cast helped glue the story together and paper over the cracks.
But I don't think films can keep doing these continuity changes if they are supposed to exist within an established timeline alongside many other films (which are all issued together in box set). It's adding to a growing sense of fatigue with this franchise. There's enough anti-Fox sentiment as it is regarding the X-Men, and poor continuity is offering ammunition to the opponents.
http://www.hollywoodreporter.com/heat-vision/x-men-apocalypse-confusing-chronology-897957
http://www.hollywoodreporter.com/he...signed-deadpool-defections-gambit-hold-945505
http://www.hollywoodreporter.com/heat-vision/x-men-movies-what-they-need-win-back-audiences-945929
http://www.hollywoodreporter.com/heat-vision/why-x-men-franchise-needs-898089
Also, critical response is not always a guarantee of good box office. You can't assume that because critics praise it, then it will be a smash hit. Just look at 127 Hours, Blade Runner, Seven Samurai and Letters from Iwo Jima.
In addition, the fan reaction to movies is far more vocal and widespread these days, because of the internet and all the various blogs and comic book movie websites, many of whose writers are also reviewers who contribute to RT ratings.
So I think filmmakers have to bear in mind mainstream fans and the geeky fans as well (if it's a comic book movie).
I disagree with Mangold's assertion that "ALL that matters" is making a good movie. That suggests anything can be changed, rebooted, rewritten, tossed out, from previous entries in the series and that no one will notice, or care.