There’s a helpful blog post here by Brian Hedges on preaching and criticism that should be profitable to both hearers and preachers.

For Hearers

Be careful. It’s dangerous to sit under the ministry of God’s Word with a critical ear. If you don’t watch your heart, you will impoverish your soul. Look for defects in the sermon and you’ll always find them. But don’t develop a critic’s mindset. Instead, come to worship with eyes peeled and ears perked for the Word of the living God.

For Preachers

Take your critics seriously. Almost every criticism contains a germ of truth. Your job is to find it. Maybe you weren’t clear enough. Perhaps the sermon really was too long, or had too much content, or was over people’s heads. Spurgeon once reminded his students that the Lord commissioned Peter to feed his sheep, not giraffes. Whatever the critique, give it some thought. You will learn something.