The Lutheran view of Mary is a lot more muted than the Catholic. Luther was very devoted to Mary, but would not recognize the modern Catholic view of her as correct (nor would most Catholics of the time). The later Marian doctrines were not popular back then, and were sometimes suppressed (things like the Immaculate conception, Assumption, and the theory that is gaining ground of Mary be coRedemptrix). The idea of Mary not dying was not something that was considered “in bounds” for much of the early Reformation, and indeed was often viewed as out of bounds.
Actually there is nothing definitive on Mary's death or lack thereof in Catholic teaching. There are two traditions (not what we Catholics call Sacred Traditon).
>>and the theory that is gaining ground of Mary be coRedemptrix<<
Only non-Catholics believe this along with a few Uber-Catholics who wish it to be so.
JPII ended that theory in the 90’s and B16 agrees with it. The Church will never name Mary Co-Redemptrix.