1918 lets see, a war was going on, there were no antibiotics, hygiene was different (in the USA).
You also had a whole lot more people who were rural, and able to stay home, avoid crowds, and take care of themselves and family members
And no global jet travel where a person sick in Hong Kong could be in NYC 18 hours later
Face it, the greatest medical system in the world can’t put tens of thousands of people on respirators, even if it would keep them alive. And most Americans will find it very hard to stay hunkered down at home for weeks if schools and grocery stores are closed
In 1918, we also did not have millions of people with HIV, AIDs and 3rd world immigrants who are sitting ducks and vectors for other diseases of opportunity that will accompany a flu pandemmic, My G Grandmother survived the 1918 flu but was brain damaged by encephalitis