[ekianjo]

You fail to see the bigger picture: - exchange of knowledge/technology - exchange of goods - exchange of cultural assets (goods, ideas and languages) - establishment of trade routes and advancement of transportation systems (roads, sea routes)

It was massively positive overall. And while the plague killed many people, mankind learned a lot from it: we lacked hygiene and we were able to identify measured to further protect ourselves from such afflictions.

[Mvandenbergh]

We didn't learn anything from it, we had no idea what caused the Black Death until well into the modern age, centuries after it actually happened.

[Fomite]

While you might argue that development was a net positive overall, we didn't actually learn a whole lot from it - plague was a recurring problem in Europe for centuries. For example, major epidemic we all think of as "The Black Death" kicked off in 1347, but there were still major outbreaks (the Great Plague of London) in 1665.

If any one disease is responsible for hygiene and disease prevention in the west, I think you can make a much stronger case for the Cholera outbreaks in the mid-1800's.