1) the kings fought the popes too much ( to the point of imprisonment)
Secular and Muslim countries still fight the Church and the clergy, and Christians(especially Catholics in General) eg. Egypt, Iraq, and China, mass killings of clergy in Mexico in the past century/turn of the 19th 20th Century, The Spanish Civil War, the list goes on…overall I think there was far less violence against the Church in the Middle Ages, at least Western Europe.
- feudal society was not able to adequately defend nations against vikings/danes (no professional army).
Modern armies/military technology has “failed” to defend people as well, for instance there are still, presumably, losing sides in wars. Moreover, modern warfare causes far worse destruction, eg. WW2, millions of people in just half a decade. It alone would have killed the entire population of Medieval Europe. There is no way war/armies are better now. Hiroshima and Nagasaki compared to a viking raid, no comparison - granted it would really be horrible being attacked by vikings…for other reasons

:knight2: the battle of Stalingrad and Berlin compared to the siege of Jerusalem, again, no comparison.
- a temptation to religious intolerance and superstition.
Nothing unique there. Temptation to religious intolerance and superstition has been around since the fall. Communism, by its nature, has religious intolerance as one of its key features. Read anything about the Soviet persecution of the Orthodox Church and its clergy. Superstition now, although different, usually involves New Age concepts, such as spiritualism, or the espousing of Buddhist and Hindu concepts, all incompatible with our understanding of God and the human soul. Not to mention the modern tendency to unquestionably accept any theory “Science”. Don’t get me wrong the medieval ages had their superstitions and idiosyncratic beliefs as well, but I doubt if they were really any more far fetched than what many people think is perfectly reasonable now.
Those are my hypothesis about what was wrong, but I’m sure others have more substantive ones.
In short, I don’t really disagree with your proposed problems of the middle ages, but I feel that since the problems that you brought up not only weren’t unique to any specific century or local in the medieval ages, but in fact persist and have often become far worse in our own times, I think you might want to reexamine what some of the unique problems of the middle ages were.