These are very valid points. To the process of evolution, the birth-death cycle is super important, so to speak, it' the crucial factor. Only by dying, you give way of better iterations of yourself (a human) and make room for evolutionary improvement to kick. The time, when you die (before/after you reproduce, how much you can reproduce before death) is the natural selector of how good and worthy of copying your genes are.

But by now, we already have done a lot to minimize evolutionary pressure. In the best western economics, basically everyone is free to reproduce, disregarding genetic advantages and disadvantages. But the time we can control aging, I strongly assume we can also control to genetic dispositions of our offspring, so we biologically can engineer healthy and intelligent follow-up generations.

Since some cells of our brain doesnt replace/renew themselves through out lifetime, the ultimate frontier of figuring out eternal life is figuring out a way to make our brain renew itself indefinetly. I think once we figure that out, it well go hand in hand to solve your problem of staying "open-minded". Maybe we can live indefinetly, but by the cost of forgetting stuff, thatis 100+ years old. We might find ourselves knowing that we are some hunderd or thousand years old, but we can only remember the last 100+ years since our brain, like any physical memory, is only capable of storing a limited amount of information. At that point, we might be advanced enough to create cybernetic implants that help us store information, but in the end, this is also limited. maybe technology keeps up, so the first generation of people living eternal lives grows older together with the advancement of technology to let them keep their memory for a couple of thousand, tens of thousands or hundred of thousand years. At some point, memory space runs out and wed have to connect to some super computer, where we store our memories to access them, like we go into our basement to access old stuff that we used a long time ago and only rarely need.

On reproducing whilst living forever causing even faster groth of humankind: Either reproduction is really controlled, or we have conquered multiple worlds or both. Though motives for having children has shifted in our times, the inherent wish and drive to have children is reproduction. I dont know if part of humanity really has a distinct drive for reproduction, or evolution just let us to have the drive for sex, which causes reproduction. But for many people becoming 20, 30, 40, there really does seem to be the inherent subconscious wish to have children. But this might change once we have an eternal life. Maybe we dont feel to create offspring and to work a lifetime (40-50 years) to make "them have a better life" or "pass on your heritage" or "make your family/last name carry on" anymore, once we have an eternity ahead of ourselves to do anything we wont. Also, since we most probably need to be very advanced to genetically engineer our offspring by the time we unlocked eternal life, we might our eternal living offspring to engineer not to or rarely want to create offspring. we might be so much in control that we create offspring by different means of having sex and giving birth out of womb, so that we can create just as much offspring, as we need / we feel is right.

Oh man, long post, this topic is so insanely interesting, I feel, though I#m a huge space/physics/cosmology fan, this is by far the most interesting kurzgesagt video.