There is a difference between "Quarantine when you cross a border" and "Shut down all commerce and tell people they can't leave their homes for months on end"
There's a difference between the death rates in those plagues and this pandemic, too. There's a difference in the amount of information we have compared to Ragusa. There's a difference between how globally connected the world was then. There's a difference in the technology we have now that allows us to continue to facilitate some sort of economy from our homes.
conclusion: this is a very contrived comparison
Indeed lockdown and quarantine are different things. The countries that have had proper quarantine eg Vietnam, NZ, Thailand have mostly done rather better with covid than those who have not eg. the UK and USA.
Had governments actually shut down all commerce and told people they can't leave their homes, this would have been over in a month.
True. But I mention this to my fellow Canadians and they have very little interest when I say it (I live in Vietnam currently). And yet at the moment they are going through the worst lockdown I've heard of: curfew at 8pm and lifted at 5am. Unheard of. Surely if they thought about it, they would have preferred to have closed the borders and waited it out. That's what COVID successful Asian countries have done.
> this would have been over in a month
Yea. Because everyone would have starved to death.
Quarantine when you cross a border requires a meaningful border.