You have a lot of good reasons to think that cynicism is the natural result of aging... maybe it is. But I'd posit an alternative, that perhaps pragmatism, rather than naive youthful optimism, is another option.
Death is real, life is hard, we struggle with health, finance, relationships, whatever. And it's all draining... but we can become cynical, OR pragmatic. I hope I'll be able to continue growing towards the latter.
Great distinction.