The real damage is not the deaths themselves here. The problem is society.
The threads that hold society together nowadays are more numerous than those of 1918, and much much more numerous than those of the 13th century Europe, and more fragile. There are many more failure points and interdependent systems at work here. We depend way more on out neighboring nation states nowadays than we did in 1918 and 1200's. Even if this disease only has a 2% death rate and only ends up killing 0.5% of the world population the damage it will cause to our long, LONG supply chains and interconnected markets will be huge. China's GDP has already taken a nosedive and as more nations resort to higher levels of quarantine and lock-down you will see that propagate further.
A while back I posted a video of a 2019 study named Event 201, where they tried to predict and simulate a global pandemic. Despite "only" killing 1% of the population this plague led to a loss of between 11% of the global GDP and somewhere along 20% to 40% of the stock markets.
ELEVEN FUCKING PERCENT OF THE WORLD GDP! To put that into perspective, the 2007/2008 financial crisis? It shrunk the World GDP by around
five. And we all remember how much chaos those 5% caused right?