Put Karpyshyn as lead writer there, and you get a game that puts Witcher 3 to shame.
Casey locking the other writers for the ending was a big mistake from him.
But all things considering, Mass Effect 3 was a very good game (up to the end). It also needs to be said that was Casey's first failure (which was still received well both on reviews and sales), and you need to remember that he is the guy who game us Kotor, Jade Empire, Mass Effect and Mass Effect 2 too, all stellar games.
On the other side, Mac Walters gave us the worst DLC in Mass Effect, to continue by making a mess of the ending of Mass Effect 3 (with the other part of the plot being essentially Dragon Age: Origins), and then getting promoted to the main man for Andromeda which in turn was the worst received (on reviews) Mass Effect game ever.
One did a mistake, the other makes failures after failures.