I meant to post this earlier but got sidetracked until now:
On 10 December 1525, at their session in Königsberg, the Prussian estates established the Lutheran Church in Ducal Prussia by deciding the Kirchenordnung, the general ecclesiastical constitution of a State Church.
https://en.wikipedia.org/wiki/Church_Order_(Lutheran)
Different Prussian holders of the privilege of minting official money committed to issue a Prussian currency of standardized quality, had debased the coins and expanded their circulation in order to finance the wars between Poland and Teutonic Prussia. However, this expansion disturbed the equilibrium of coins circulated to the volume of contractual obligations, only coming down due to a harsh depreciation of all existing nominally fixed contractual obligations by inflating all other non-fixed prices measured by these coins, ending only once the purchasing power of every extra issued coin equalled its material and production costs.
Understanding this important bit of state/aristocratic economic history (which I lifted from wikipedia) sheds a very important light on how Martin Luther described the need to shift away from the Church in Rome and develop a new one that had less (or different) ritual pomp and circumstance.
Luther wrote, in his usual logorrheic manner, that "this and all other forms were to be used in a manner that where they gave rise to a misuse they should be forthwith set aside, and a new form be made ready; since outward forms are intended to serve to the advancement of faith and love, and not to the detriment of faith.
Where they ceased to do the above, they are already dead and void, and are of no more value; just as when a good coin is debased, sad or retired on account of its abuse, and issued anew; or when everyday shoes wax old and rub, they are no longer worn, but thrown away and new ones bought.
The form is an external thing, be it ever so good, and thus it may lapse into misuse; but then it is no longer an orderly form, but a disorder; so that no external order stands and avails itself, as hitherto the papal forms are judged to have done, but all forms have their life's worth, strength, and virtues in proper use; or else they are of no value whatsoever" (Werke, Weimar ed., xix. 72 aqq.).
So, contemporary Protestant theologians/scholars read Luther as teaching about putting the spirit before the letter and not continuing with the debased ritual practices of the established Church. But those readings are mostly wrong. Luther was not being metaphorical; he was literally warning people about the economy and the need to reorganize the minting of money.
https://en.wikipedia.org/wiki/Prussian_estates
Lutherans themselves did not begin to use the term Lutheran until the middle of the 16th century, in order to distinguish themselves from other groups such as the Anabaptists and the Reformed (Calvinist) tradition. When doctors/dons of the Church (Roman) used the word earlier it was as a heresy, the same way that other heretical doctrines were named after a prominent proponent, like Marcionism or Nestorianism (or more recently, Mormons and Jehovah's Witnesses).
When Pope Benedict XVI was still Cardinal Ratzinger, he mostly let Protestants off the hook for the sake of neighborly relations. Here's a nice paragraph by him praising the value of certain Protestant insights:
https://en.wikipedia.org/wiki/Heresy_in_the_Catholic_Church#Modern_Roman_Catholic_response_to_Protestantism