I read a current research paper (abridged) sorry I didn’t save the source but found it easy enough on non-academic Internet that proposed that the Spanish flu (SF) was fairly mild - the high fatality rate can be, possibly, put down to a world population weakened by WW1. This looks likely as, even though Covid 19 is far more contagious, the mortality % rate is a lot lower than SF - experts say that the population of Covid infected people is not known and is probably higher than conservative figures suggest.
Don’t forget also that the reason SF is called Spanish is because it was the only country to report it and keep records so the evidence base is sketchy to say the least.
Again, I’m not aware of any coronavirus vaccine and we’re at number 19 so these messages are somewhat confusing.
Without testing we will not know how many people have had it - I know a person who has had it (tested) and didn’t even know, I had the symptoms about 3 weeks ago. They were very mild and I carried on with my physical job but later when I saw what the symptoms were it made me think.
So herd immunity may well be on the way.
Also viruses usually mutate into a milder form and our antibodies can easily cope with these - I suspect SF is still around with no or little effect.

I’m not a “we’ll all be back to normal in 3 weeks” person, I think things will be difficult for 6 months or so ( longer financially) but...... these things have happened before and I certainly don’t believe it’s going to change the world - human nature hasn’t changed during recorded history - over 2000 years.
In 2 years it’ll back to the same old same old -