So when you read him, note the dates. Through till 1517-18, you've still got an essentially Roman Catholic Luther. Move to the 1520-24 and you've got the anti-Romanist Luther. It took the battles after 1524 to make Luther realize how much Rome itself served as bulwark against a rampant spiritualization of the Holy Sacraments. By the time you to the Catechisms (1528 and beyond) you've got a Luther who has contended against both dangers, and presents a more balanced picture of his thought.
This method of reading Luther is far from novel. It is, in a sense, sanctioned in his intro to the collected Latin works. He warns that the papal leaven was rife in him for many years.
What is truly curious and delightful is when a thought expressed in the early years carries through all the intervening years. I'd suggest THAT's a key point in Luther. A much unexamined point in the great Reformer would be his take on the communion of saints, which remains essentially unchanged from the great document on the Eucharist in 1519 to his writings on John in 1528 to his writings on the Church in 1539. It is a thought sadly missing in much of Lutheranism today.