This was the standard of care for chickenpox (herpes zoster, aka shingles) until 10 or 20 years ago, for example. Sure, the mortality rate is lower, especially among healthy children.
You're off by a decade and possibly two. I'm older than 20, I was vaccinated for Chickenpox. The vaccine has been commercially available for 35 years.
So I'd reiterate the question.
There may have been a vaccine 35 years ago (I'll take your word for it), but it was not the standard of care even ~25 years ago.
(And to be clear, I'm not advocating for exposing people to COVID, at all. You asked a very broad question upthread with an easy counter-example — chickenpox — and I provided the counterexample.)