You're not wrong. Disease is just one club in Mother Nature's golf bag she uses to keep all populations within sustainable sizes -- including humans.
HIV was/is a "driver" -- taking out a huge number of people in a relatively short time, often by allowing other, often rare, diseases the ability to flourish in a comprised immune system.
Look at all the natural disasters: tsunamis, earthquakes, floods, hurricanes. tornados, heat waves, blizzards, high winds, .... so many types of weather-related situations that wind up killing humans and other animals.
Heck, you could toss in mental illness. Committing suicide or killing other people for this or that insane reason are just more "culling methods" Mother Nature throws at us.
Man has the advanced technology to counter most diseases we know of. Still, there's no real way to prevent cancer. All we can do is fight it when we find it in time. Same for new viruses. It takes time to learn of its weaknesses and capabilities. Until we know, any meds we try on it could be making it stronger for all we know. That's precisely how antibiotic-resistant strains of bacteria evolved.
Your comments made me think of the theory of symmetry in nature. It also made me think of Malcom’s comment in Jurassic Park, “Life finds a way.”
As the human race has continuously found ways to extend our life span, nature has continuously acted to counteract it. Balance, I suppose.
As a father to a young child, I just hope things end up being okay eventually. I now know how my parents felt as they watched me grow up, and I hope that things blow over like they have in the past. Nevertheless, I’m taking the “Optimistic, but prepared” route. Trying at least.