There's something that I don't think gets discussed enough when this topic is risen. One reason why death is good is that the ideas of old people die with them. Often, it's the only way to scourge ourselves of bad ideas. Imagine a country of people still stuck in an 1850s mindset.
I believe the idea that people never change is probably somewhat misguided. Right now, as a culture we reward people for doubling down and never admitting to being wrong. And no matter how wrong a person is, if they are loud enough, they'll always have supporters.
That culture would probably begin to change with the advent of life extension, because you no longer have to make your life about one thing, this one card you have to choose once and then play until you're dead. I admit it's somewhat idealistic, but I hope we'd be more rational in the long term. Being alive does mean constant change.
But even if it doesn't turn out that way, there are certainly a lot of important voices we have lost over the centuries, a lot of ideas and thoughts that we never even got to hear about, and people who would have contributed great things if they had lived long enough. I for one would gladly live in a world where some ancient philosophers are still alive.
Let's go with the worst case and pick, oh let's say religious bigots, they'll somehow muster the intellect to extend their lives, remain prolific spouters of nonsense, and never change for 10000 years. It's a small price to pay to live in a society where I and the people I care about get to live 10000 years! I could just filter the bad elements out, just as I do today, and everything would be absolutely fine.
An argument could be made that those people are bad for society because they hinder progress or steer it in destructive directions. But on reflection, those people carrying 2000 year old ideas in their heads are here and active in our society right now, and we're still moving forward.
* Brain cells die.
* Brain cells hold ideas.
* We need to regenerate brain cells to continue to support the brain past 80-90 years.
* Each new brain cell will probably adopt the ideas of the surrounding culture.
So I would suspect that over time, an aging but renewed brain will adapt to the conditions of the culture it lives in. Some brain cells are more stubborn than others, but a serious and dedicated effort to not adapt will be met with obvious survival constraints.
The current generation of old people have to die and they will. Some of them actually hold modern views and have bothered to keep their minds active from youth into their old age. The ability to change one's mind and empathise with modernity can be learned.
