> Comparing oranges to oranges, if SARS-CoV-2 had spread in 1918, it's likely COVID would have been a bigger killer than the Spanish Flu.

The lower bound on Spanish flu's IFR is 3%. Covid's IFR is around 1%, and almost all of that is in old and sick people. Spanish flu killed far more at far younger ages. Had covid hit a century ago, its IFR would likely be lower because those hit worst by the covid (the old and sick) would have already died of something else.

Again, Spanish flu infected 1/3rd of the world and killed at least 1% of the world population. It was the last time in history that human population declined over a year. Even in 3rd world countries, covid can't approach that level of lethality.

It's worth noting that you're comparing the dynamics of a particular pandemic in a particular year - we don't know for sure how the Spanish Flu would have behaved in a different time. There are reasonable theories that the Spanish Flu had been spreading for years prior to 1918 - perhaps as early as 1915, with few noteworthy "pandemic" level deaths before going nuclear in 1918. Even the cities that were hit by the first wave in 1918 tended to do much better, before the more deadly strains began to spread - contrary to pandemic evolution and driven largely by the dynamics of war. 1918 was a perfect shitstorm - malnourishment was rampant at a global level from the prolonged war, young active soldiers carried the infections worldwide, the sickest soldiers (ie, the most deadly viral mutations) were transported to crowded field hospitals, infected soldiers passed on the virus to soldiers recovering from poison gas attacks, the pathogen was not identified for the longest time and bacterial agents were focused on instead, the refusal of national governments to recognize the pandemic, and so on. It's a fair assumption that those conditions would have greatly exacerbated a 1918 COVID pandemic as well. Yes, COVID deaths have been highest in the elderly - but co-morbidity is important as well. A 1918 population would have fared poorly with SARS-CoV-2.

I'm not trying to imply that Spanish Flu was not a killer - my home country of India suffered ~ 13 millions deaths. Yet the policies of the Colonial Administration also made a bad situation much worse. My suspicion is that given those circumstances, COVID would be just as bad, if not worse. At this point we can only speculate.