Weird situation. I mean, we've known for a while now that, essentially, the buck stops with Feige. Marvel may bring in some visionary directors, but it's clear they do things differently and Feige has a lot more control over things like the script than a typical producer would. Whether good or bad, that's how Marvel does things and we know the level of control they expect to have on all their movies that build towards the MCU as a whole.
If Wright's script didn't meet what Feige personally wanted for the overall MCU, then fine. But it doesn't make sense to me that it wasn't a dealbreaker for either party until the final re-write, after all those years. They must have done some crazy stuff to Wright's script for him to walk after all that time - and to do it all last minute like that is a shit move on their part.
Rumours had come out a while ago that Wright was pushing back against incorporating Ant-Man into the rest of the Avengers cast, and when they had announced production and a release date I figured all that stuff had been ironed out. I wonder if that was still the main point of contention - maybe Wright's final script still kept the movie too "standalone" and at this point, and after the success of The Avengers and its follow up solo films, the last thing Feige wanted was to stick one of the core Avengers cast members in a standalone environment. It's bad enough that they've written one of their major characters (Pym) into a time period where he can never be on the Avengers team.
I dunno if we'll ever know 100% of what happened here but there was probably a lot of tension on both sides and if Wright wasn't happy directing a film that didn't match up with his vision and original script, then it was better for him to walk. Marvel will get the movie they want in the end, it may not be the same film that fans of Wright wanted, and it will probably end up a bit more "homogenized" as they said, but I can still see this being a worthy entry in the MCU as long as they still to justice to the character.