If you got measles as kid with a healthy immune system usually you’ll do fine, although you’ll probably average being sicker than with the other ‘routine childhood viruses.’ But if you get it first when you’re older, sicker or when your immune system is otherwise not full strength it does kill some and certainly can knock healthy folks for a loop. Of the ‘old world’ diseases imported to the ‘new world’ it probably killed the next month after smallpox (itself once the worst of the ‘routine childhood viruses.’)
Smallpox was never considered ‘routine childhood disease’.
It was not that contagious and most people got it at adult age (e.g. Pres. Washington).
On the other hand, since measles are the most contagious disease around, basically everybody got is before the vaccine was developed. We are all (older folks) measles survivors or descendent of measles survivors!
I believe that not getting measles in childhood was kind of scary, because the older people had more problems with the virus.
The worst affected were the Native Americans and Hawaiians who were not exposed to it before the contact with Europeans. Measles indeed wreak havoc in these communities!