It is a misconception, usually called 'Christian Dark Ages' at /r/badhistory that there weren't any advancements. You can find a multitude of posts about it in. In fact, there were quiet a bit of scientific advancements during that period, especially in the Middle-East and India.

Even in Europe, there were quiet a bit of advancement. The Catholic Church, who is often presented as anti-science funded scientists.

The most important word in your description of the video is "seems."

If the video didn't include scientific and engineering achievements during any period, it's because the makers of the video chose not to include them.

It's really difficult to give an overview of the history of science, I'll admit to that readily, having done it myself while designing a survey course in grad school intended for engineering students required to take a history class. It was what my committee chair called an "arrows to atoms" course and covered as much of the history of scientific achievement as I could fit into a single semester, and I admit with some regret that I made a jump of several centuries in a single week.

But it's not because nobody achieved anything in those centuries. It was a painful decision based purely on restrictions on time and the number of books I could assign. The same is true of a lot of histories of science. You have to cut some stuff, and for various reasons, some defensible and others less so, the medieval period gets the short straw more often than anyone would like.

During the Muromachi period (1392-1576) the katana (meaning cutting edge up) was developed in Japan which was an advancement over its precursor the tachi. It's such a great invention that they are still being made today. It's use in warfare as a primary weapon declined in the meiji era.

Edit: You are going to down vote me for being right?