That takes care of the spiritual punishment, and that is enough for that. I am grateful he did that, and praise his name.
HOWEVER, He didn’t take care of the temporal punishment which we are still under.
Let’s imagine that Adam and Eve did not sin and remained there. Do you not think their children would be allowed to stay in the Garden too? Of course they would. Using your reasoning, they would have to be kicked out because that’s how things are now.
God gave the gift of the Garden of Eden to all of humanity, since Adam apparently represents all of us in our temporal state. When he took it away, he took it away from all of humanity, and punished all of humanity.
Can’t have it both way. If Adam represented us all as the Catechism says, then the Garden of Eden was a gift to all of us. Taking away that gift is a punishment that God put on all of us.
And thus we are punished because of Adam’s sin, and yes, that is unjust in a negative way. We do not benefit.
BUT we have Salvation in Christ’s name which is unjust but in a positive way. Christ paid the penalty and we benefit.