What was Adam's punishment?

Adam and Eve were placed in the Garden of Eden and were forbidden from eating from the Tree of Knowledge.

Eating from the tree of knowledge would make one aware of evil in addition to good.

The snake tempted Eve to eat fruit from this tree. And Eve even shared this fruit with Adam.

For their disobedience, Adam and Eve were banished from the Garden of Eden and they brought sin to this world because they and their descendants gained the knowledge of evil.

In my view, God forbids them to eat from the tree of knowledge as they would lose innocence by acquiring knowledge of evil.

And isn't innocence a great trait in individuals?

Innocent people are child-like and God wanted humans to be child-like as we are his children.