True enough. There have been plenty of setbacks for mankind along the way. Its interesting to consider where mankind would be without the burning of Alexandria, the dark ages and black death etc.
On the other hand, the dark ages seemed to have sparked something and technology exploded out of it.
Of the three items you mentioned, 2 can be directly attributed to islam. (The Black Death was allegedly spread to Europe when muslims laid siege to a city and hurled an infected corpse over the wall. Rats and fleas escaped , carrying the disease with them. The burning of the Alexandrian Library was due to the fact that it contained pre-islamic knowledge and lore.)The Dark Ages can also be linked, if one works at it!
I don’t have links or articles to these theories; I just have heard it said over the years.
Perhaps those really aren’t setbacks, but necessary events to get us to where we are today.