The simple answer as to why "The Chart" is bad history is because it attempts to grade scientific progress through different eras based on an exceptionally vague notion of what scientific progress really is.
Productivity per labour unit, level of education, and average lifespan were all lower. While you can't perfectly measure it, it's fallacious to say you can't measure it at all
It also, famously, implies Christianity and "The Dark Ages" (which is it's own little bit of bad history) were intertwined and had a causal relationship with one another, while purposefully ignoring the fact that the Western Roman Empire had collapsed at the same time.
Part of the reason the WRE collapsed was due to christianity, was it not?
The civilizations built up a few hundred years later were christian, and advanced more slowly until ~1400
The reality however is that what we might consider "science" had been more or less stagnant for quite a while prior to the collapse of the WRE. There were of course developments, but it's not as though the WRE was only a step or two from developing the steam engine or something.
See my thing on plumbing. Also, productivity was higher. And the institutions that existed in Rome were superior to feudalistic systems.
What's important to remember about the early medieval period is that the fall of the WRE left a power vacuum that had to be filled. It took a while for these things to happen, and while there's a power vacuum, travel is more dangerous (than it already was, and it was no picnic under Roman rule), information spreads less quickly, and there is less leisure time to pursue academic interests for more people.
Medieval Catholics felt that God was a rational being, and as a rational being, he created the world and the heavens under rational laws, which we could understand through observation and thought. Medieval natural philosophers (as they were called, these were the precursors to our modern day scientists) strove to learn as much as they could about the natural world, which would as a result, allow them to learn more about the nature of God.
Again, I'm not saying that this wasn't a phenomenon, but we're talking about trends here.