The goal is to lengthen human lifespan? Like the planet doesn't have enough humans already.
We've populated large portions of the planet that we really have no business living in without climate controlled indoor environments. HVAC is also a huge energy suck with all the externalities that come along with it. If we were to really want to cut energy use, for example, and climate control had to go we almost certainly couldn't continue to sustain as many people as we have today.
I'm with you, but let's just say it.
People, as a whole, don't want to make the changes we all know would make the world better.
People, as individuals? While there are exceptions, the reality is a classic tragedy of the commons. Individuals generally won't accept a short-term drop in their standard of living while watching their neighbors refuse to do the same.
It is what it is, frankly. We can and will change our lifestyles at the very last possible moment. Let's hope it's enough.
Think of the aboriginals and nomads roaming the deserts and the inuit in the icy north. All before hvac.
And hvac isn't really as much of an energy problem as heating is. Because when hvac is needed it is during a time of abundance of sunlight.
I can't imagine Canada or Europe could support their current population sizes without HVAC, or refrigeration, or pesticides and herbicides.
The list goes on, but in my opinion and understanding there is too strong of a correlation to ignore between those types of modern inventions and population growth.
https://www.populationpyramid.net/france/2026/
If they keep it up, their population will remain stable up to the 22nd century. There will be no further noticeable ageing and thus no threat to anyone's retirement.
Just imagine how many more grandpas and great grandpas will be around for you to shout this at.
The problem with the population isn't (yet? only?) the absolute number of individuals but the age distribution. Most societies rely on young people to support themselves and the old, and this only works if there's a good balance between the numbers of each. Living longer isn't guaranteed to offer a longer productive period. We might just end up with more old people in need of support and not necessarily more children. This is already a major problem today in most developed countries.
There are probably so many more factors to consider. Like the psychological impact of living substantially longer. Even things like that crappy boss who won't retire from another 60 years, the dictator who won't die for another hundred years, or any number of the many society destroying tech CEOs getting to entrench themselves for decades more.
This will happen no earlier than the 2080s. The world population is expected to increase every year until then. We will add nearly 2 billion people in that time. Consider that the entire world population was less than 1 billion for all but the last 221 years.
I continue to not worry.