Thranduil is one of the most powerful elven lords of the Third Age of Middleearth. Moreover, he was the only one who held the title of king. He ruled over the rather large (by elven standards of the Third Age) nation of Mirkwood elves and stubbornly resisted the growing influence of Sauron's forces.
At the same time, Thranduil had little contact with the rest of the Elven lords, who actually opposed Sauron as well. Thranduil was not summoned to the White Council, no global plans of the Forces of Light were discussed with him, no intelligence was shared, and in general it was as if he had no contact.