It's not really an affliction like that, but truly is more cause and effect. The reason is it follows from the doctrine of creation ex nihilo, for the Fathers elucidate that mankind does not have power in itself to remain incorrupt, not to die, not to dissolve, not to change, etc, for they were made out of nothing and out being is constantly dependent on God (as are all things). We began in change (non-existence to existence) and so are subject to it, and dissolution again, unless God keeps us. The thing being that we have free will and can turn towards our "natural state of non-existence" (for evil is not but good is, and ultimately as the Lord Jesus said "there is none good but God") or turn towards Eternal Existence (which is what God is). It is rightly compared to how if you turn away from drinking water which you need to not die then you will die, or if you turn away from breathing air which you need to not die you will die (and I don't think anyone calls this "vindictive"). In the same way if you turn away from what is keeping you incorruptible you'll become corrupted and slowly begin to break apart and dissolve into nothing (and this is sickness, pain, forgetfulness, aging, death, and so on).
Adam and Eve were the only two human persons and they both became corrupt (so this was not done to "us" as if all of humans to exist were present then and some didn't become corrupt, if that was the case then not all of us would be born dying already, some would not have fallen), then after that they began to reproduce sexually in our mode (hilariously called in one ancient text "unclean rubbing"), so their children could not but also be like this, which is why I compared it to your parents having a genetic disease before and you can't help but have it just because you are their children.