The problem is actually a modernist Renaissance focused mindset, with the logic being "wow the Renaissance and Enlightenment sure were awesome, the Middle Ages must have really sucked". And while it is true that the Renaissance was a flurry of invention and renewed interest in ancient learning, none of said ancient learning was unknown to Medieval scholars and in fact they helped preserve it. They just weren't at a point where they could do much with it beyond what the Greco-Romans already did. In addition, a lot of the inventions and innovations that did take place during the Middle Ages are perceived by modern eyes to not be that impressive, despite the fact they were marvels of the age - the biggest example of which was the humble mechanical crane, which the Greco-Romans dabbled with but the Medieval Europeans perfected. And there were all the clocks and early automata that laid the ground work for what happened in the Renaissance and Industrial Age.
If you consider things purely from the perspective of someone living in the Middle Ages, a lot was being done. But from the perspective of someone living in the 19th century - which is where much of the American perspective comes from - then they weren't doing things fast enough.