From quote in that post:

"One of [the Middle Ages'] characteristics was that 'reasoning by analogy' was rampant; another characteristic was almost total intellectual stagnation, and we now see why the two go together.

There's no reason to spread such myths about medieval history.

The main characteristics of the Early Middle Ages were low population densities, very low urbanization rates, very low literacy rates, and almost zero lay literacy rates. Being in a reference class of times and places with such characteristics, it would be a miracle if any significant progress happened during Early Middle Ages.

High and Late Middle Ages on the other hand had plenty of technological and intellectual progress.

I'm much more surprised why dense, urbanized, and highly literate Roman Empire was so stagnant.