Given that there are thousands of Protestant sects, it is impossible to speak of a single Protestant view of the Middle Ages, so I will have to speak in generalities by necessity. I will also confine myself to the English speaking world.
In many ways, the Protestant critique of the Middle Ages mimics the atheist/humanist critique by emphasizing the corruption of the church and the ignorance of the populace. However, for Protestants the main problem with the Middle Ages that the medieval church was “doing Christianity wrong,” especially by keeping the Bible away from the masses. As I explained in the previous installment, it would have been impossible for every person or even many people in medieval Europe to have a Bible even if mass literacy was a thing, but then again, I also don’t think that having access to a Bible does much for ones faith or morals.
Protestants also take issue with the various extra-biblical practices that the medieval church encouraged, most notoriously indulgences (which are never went away, BTW), but also the cult of the saints, Marian theology, the use of pictures and statues during worship, pilgrimages, relics, purgatory, monastic orders, etc. John Calvin’s “Treatise on Relics” is probably the best explanation of why some of these practices are so offensive from a Protestant standpoint, but the argument can generally be summed as “it’s not in the Bible” (Catholics, of course, can come up with their own Bible verses to support the veneration of relics, Marian devotions, or what have you, but that’s neither here or there at the moment). While the Reformation did sweep away the superstitions associated with Catholic sacramentalism, the masses in Protestant countries didn’t became any less superstitious; rather, they just became superstitious about different things. The Bible, in particular, became an object of magic, veneration, and superstition, especially since most people still weren’t literate in the post-Reformation era. After all, if the Bible was literally “the Word of God” then how could it not be the object of awe and a source of potent magic powers? In an agrarian, pre-literate society, sola scriptura is practically an invitation to Biblical superstition.
In Victorian era England, some dreamy reactionaries began to reappraise the Middle Ages, the most famous being G.K. Chesterton and Hillaire Belloc. The social, political, and cultural chaos left in the wake of the Industrial Revolution left some wishing for the stability of the Middle Ages, when everyone knew their place and the church provided for everyone’s physical and spiritual needs. The guild system in particular was seen as an ideal way to defuse both labor militancy and the exploitativeness of capitalists, and influenced the development of distributism. The Oxford Movement to “Catholicize” the Church of England was also based on a desire to return to the unitary innocence that the pre-Reformation church was believed to have. Indeed, the notion of “Europe is the Faith and the Faith is Europe” is based on the overly simplistic view that medieval Europe was completely united under the benevolent watch of the Catholic church, whereas the Reformation led to fragmentation and heresy. Of course, the Protestants who fully bought into these romanticized views of the Middle Ages and medieval church tended to “jump the Tiber,” like the afore mentioned ChesterBelloc and John Henry Newman, rather than remain Protestant.
Some Protestants on the dominionist fringe seem to be into the idea of an agrarian society ruled by religious law that could be interpreted as being somewhat analogous to a Protestant Middle Ages (here, I’m thinking of figures like Gary North, R.J. Rushdooney, and the disgraced Doug Phillips). I suppose for such people, the Middle Ages were fine in theory, but had the wrong theology.
In general, I think that most Protestants tend to take the view that the medieval church was a deviation in some form or fashion from the purity of the “early church.” As with Jesus himself, there isn’t any independent documentation about the nature of the “early church,” so it tends to take the form of whatever a person desires in his or her ideal church; those in the peace church tradition imagine the “early church” being like a Quaker meeting or perhaps a Mennonite service; those in liturgical churches envision an “early church” more like what conservotrad Catholics might come up with, albeit shorn of those elements they deem extra-biblical; evangelicals see an “early church” focused on preaching and teaching; gnostic-inspired Christians think of the “early church” as a group of individualistic truth seekers who were eventually harassed out of existence by the “orthodox Christians”. Maybe the “early church” was all of these or none of these; the historical record is scant on this matter. However, all of these conceptions of the “early church” agree that the medieval church was a corrupt version of the purer original version.
While I would agree that the medieval church was a corrupt institution, I would also say that the church — Protestant, Catholic, Orthodox, or otherwise — has always been corrupt and always will be. What form the corruption takes will simply change depending on the place, time, and culture. Looking backwards to a “golden age,” whether in the Middle Ages, late antiquity, or the 1950s is a waste of time, and distracts us from tackling the problems that we have in our own time. Given how many problems are deserving of our time and energy, indulging in nostalgia is a delusion we can ill afford to entertain.