In a way, the church did do a lot of good during the dark ages. While the classical civilizations were collapsing everywhere in Europe, the monks were the only ones that kept the records. The church was the only organization that preserved the engineering know-how at the time.
The problem came in when the church didn't want to make public what little knowledge they had left because they knew that knowledge was power.
For the common serfs, who made up the main bulk of the European population at the time, life was absolutely terrible. The hope for something better in the afterlife was probably the main attraction the church had to offer. For the lords and knights, faith was a way of keeping the peasants in line.
Ok, to the point. I think YECs don't fully appreciate just how harsh everyday life was for the common serfs and peasants during the dark ages. To the YECs, the one thing that was most desirable for them happened during the dark ages, total faith in religious doctrine. And I think what was even more attractive about the dark ages to the YECs was that the it lasted for so long. 800 long hard years of bliss, when science was declared plasphemy.
Nowadays, we actually need to go to school and learn what had already been invented and what had already been discovered. Things are no longer as simple as making up answers to satisfy people's curiosity (like the way certain adults make up bogus answers to answer their children's questions). We actually go out and investigate, experiment, share our findings with one another, and try to explain the events without having to resort to lazy thinking of goddunit.
200 years of scientific inquiry is a lot of knowledge to absorb, and I suspect very much that this is why YECs are so uncomfortable with science these days. They can no longer read a sentence to learn a particular subject. They actually have to go through years of schooling and hands-on experience to just scratch the surface of what's out there. Imagine how scary this all is to someone that has always been making up answers to appear "wise". Nowadays, people can actually call on their bullshit.
A return to the dark ages is exactly what YECs want simply because they'd be the wisemen. They'd be the ones that everyone else looks up to for all the answers. They'd be the ones that can order the next inquisition. And by golly, they'd be the ones to do something that previous inquisitors tried but failed to achieve: exterminate the cats!