Why was Ubisoft able to make the genre change but not BioWare?

Yeah...I can't speak for all their sports games but the FIFA series has become noticeably buggier since the switch to Frostbite, honestly I think Frostbite is simply too difficult of an engine to work with if you're trying use it for anything that isn't an FPS. Apparently the Visceral team was also having issues with the Frostbite engine before they were shuttered and their game subsequently put on ice. I imagine much of Anthem's 6yr dev time was devoted to getting Frostbite to work with their vision....

Edit: Here's a quote from Amy Hennig that sheds some light on the difficulty of work with Frostbite: "...we obviously had to take the Frostbite engine, because there was an internal initiative to make sure everybody was on the same technology, but it was an engine that was made to do first person shooters not third person traversal cinematic games. So building all that third person platforming and climbing and cover taking and that stuff into an engine that wasn't made to do that. We did a lot of foundational work that the teams are still benefiting from because it's a shared engine, but it's tough when you spend a lot of time doing foundational stuff but then don't get to go ta-da! You know here's the game."

Pretty much sums things up, making dynamic third person games with Frostbite sounds extremely difficult, combine that with trying to add in cool the new things such as procedurally generated worlds for MEA or persistent shared world experiences for Anthem probably ate up quite a bit of dev time and in MEA case resulted them having to straight up scrap their idea.