Kitty Pryde's phasing properties are an enormous screw up.  Nothing matters in the X-Men world anymore.  Don't like how things went down?  No problem, just send Wolverine back to fix it.
How annoying is it when you read a story or watch a TV show and at the end it all turns out to be a dream?  That's what they've done to X-Men.  Nothing that happened in all those previous films we watched actually happened.  That was a different time-line and none of that matters anymore.
 
Just trash those old Blu-Rays.  That didn't happen.