“things.” The Hebrew word dabar here is very broad and means “things,” “words,” and “matters.” It seems to be in the context of contending with God (Ecc. 6:10), and so words and things fit well, and “things” fits well with the next verse (Ecc. 6:12) as well. People can contend with God, and use more and more words and things in arguing against Him, but they have no effect other than increasing the pointlessness of the argument.
“pointless.” See commentary on Ecclesiastes 1:2.