Though we disagree on the papacy, Mary, purgatory, priesthood, Eucharist, imputation (and plenty more), I believe unity on some level would be possible were it not for the fact that the foundation of the division is over the nature of the Gospel of Jesus Christ itself. But because the Gospel itself is at stake, unity is impossible. In fact, it’s not biblical. When Rome believes and teaches that salvation is by grace alone, through faith alone, in Christ alone, to the glory of God alone we will have something to discuss.
There are “big tent” and “pup tent” ways to formulate doctrine. I like this one: Faith alone saves, but the faith that saves is not alone.
I doubt that most Protestants are that Lutheran. That most Lutherans are that Lutheran.
And yet Christ tells us that we will be judged according to our deeds.