Why does Paul say impressive-sounding speech is worthless in church?

Les explains that Paul's point is communication: what good does it do to come with high-sounding, intellectual, perfectly formed statements if people don't know what you're talking about? The Word of God is simple, and he asks prayer to keep these truths simple enough that a six-year-old can understand them. He illustrates this by explaining the gospel plainly to a man who had never heard it, so the man could leave with no doubt about what it would take to gain heaven. Paul also notes that there are many kinds of voices in the world, and none is without signification; even animals communicate, and their sounds are not gibberish when the hearers understand.