The 30% mortality rate you quote is for people who develop severe symptoms. Most people who get it have no or mild symptoms. In addition it’s a extremly rate disease to catch and highly unlikely in most locations Delta flies. If your not vaccinated you are restricted from flying to yellow fever zones. You are far more likely to get hit by lightening than to catch yellow fever. When the vaccine first came out there was lots of opposition to it. That opposition was actually somewhat correct as there were lots of issues. Far more than with the covid vaccine. Problems were fixed and Yellow fever was virtually eradicated until people quit getting the shot as it was viewed as no threat.

“Yellow fever virus is a mosquito-borne flavivirus that causes yellow fever, an acute infectious disease that occurs in South America and sub-Saharan Africa. Most patients with yellow fever are asymptomatic, but among the 15% who develop severe illness, the case fatality rate is 20%–60%.”