Teleology in biology is a fallacy. Even some textbooks may misleadingly suggest, even when it's not intentional, that an adaptation may have happened voluntarily (misused language). But that's not what happens in biology, except for the influence that the mind can have on natural selection. For instance, humans with intelligent brains and an incredible ability to adapt, can "cheat" death by inventions and attain a rather stable equilibrium where evolution does not appear to happen, or has become extremely slow. Punctuated equilibrium means that at times some groups evolve very rapidly to then stabilize at other times when fit to their stable enough environment. "Adaptation to needs" just means some lines dying off when unable to survive in said environment (which is why it's called selection). Most species that existed are extinct. We call "extant" those that aren't.
As some noted above, something very similar to "not getting older" can happen, sometimes a cell mutation causes it to no longer die off, where apoptosis fails. When such cells proliferate they produce tumors and cancer. That's in a single organism and distinct from inheritable mutations that if not harmful enough may subsist in future generations. Individual organisms don't evolve into other species, groups do over time. An incredible example is the radiations around a large island or continent, where many animals known to be related to eachother diversified. Close enough, they're still sexually compatible. Far away enough, they may no longer be, or produce sterile offspring. In some cases if one is suddenly moved, it may also not be adapted enough for the type of food available or the temperature and places where they can nest and hide.
Humans have a certain level of awareness making them try to understand death. The entertainment of eternal life fantasies is a way to deal with the difficulty to accept it, as well as to deal with our habituated memories (we could say that a being close to us that died still "lives" in our memories). If biological beings, animals, were really immortal, it would not be compatible with the natural ecology around us that also produced us. It may not matter if some individuals could live much longer, since it's not natural it may be harmful if everyone could suddenly live 1k years or more: we'd have to deal with those environmental needs. But we already mismanage the environment and some economic forces are causing resistance and weaponizing ignorance against progress. There are other ethical considerations: is it right for a particular elite to live much longer if they require so much resources to allow them to, at the expanse of wellbeing for many other young people? Why wouldn't they have the same right to life and a clean environment, especially if the incredible wealth the elites have could allow it? We already face that problem now, with very mortal beings. Some wealthy narcissists believe that the world owe them everything and don't want to invest back in the system that allowed their comfort and wealth in the first place. It's even a challenge to make them pay their taxes to manage the existing infrastructure.
