What is ironic about the curse polyphemus calls down on Odysseus in The Odyssey?

Polyphemus, angered that Odysseus has blinded him, implores his father, Poseidon, god of the sea, to avenge him and prevent Odysseus from returning home to Ithaca. Poseidon reluctantly agrees and curses Odysseus to wander the seas for many more years. The irony in this curse is that while Poseidon is trying to hinder Odysseus's return home, he is actually helping him. If it weren't for the curse, Odysseus would have returned home much earlier and likely missed the valuable wisdom and skills that he gained from his travels and experiences during the extended journey.