For me the question is how many children are we willing to accept as fatal outcomes before we are willing to say a vaccine is required.
In the US measles related complications are typical:
Hospitalization is 1 in 4 cases.
Swelling of the brain 1 in 1000 cases.
Death 1 in 1000 cases.
https://www.cdc.gov/measles/about/complications.html There was one documented measles death in 2015 in the US.
Is that dead child enough to say "we should have prevented that particular death from that particular disease"? This statement is not intended to guarantee the child, who was otherwise healthy, would have lived, it just means they would not have died specifically from measles.
Most people I have talked to don't think measles can kill.
Of the people I know who don't think measles vaccination is a big deal have not had or known anyone that has had a child die from them.
So since only 1 in 1000 unvaccinated children die from measles is that a low enough mortality rate to consider a vaccination unnecessary?