You can exchange the poetics in Mor Dhona for Ironworks accessories (and the paladin shield). Then, take those and exchange them for Grand Company Seals at your grand company.

You can use the Grand Company Seals to buy things necessary for Anima weapons too. "Kingscake, Adamantite Francesca, and...i forgot what else".

Or, you can exchange poetics for "Unidentifiable" items. They are called like "Unidenfiable Ore, Bone, Shell, and...something else".

These are needed for the Anima weapon.
If you aren't interested in the Anima weapon, I would still exchange them for accessories and then grand company seals, which can be exchanged for ventures, cordials, crafting items, etc.

All of which can be sold on the market board for cash.