But God chose what the world considers foolish to shame the wise. God chose what the world considers low-class and low-life--what is considered to be nothing--to reduce what is considered to be something to nothing.
We shouldn't go around bragging about our accomplishments. In the first place, God is not looking for accomplishment-exclusive kind of people. And, secondly, God chooses people because God can use them for God's purposes.
Again, from the CEB:
It is because of God that you are in Christ Jesus. He became wisdom from God for us, and he met all religious requirements for us; he dedicated us to God, and he delivered us.
Then, in verse 31, "This is consistent with what was written: The one who brags should brag in the Lord!" which alludes to Jeremiah 9:24, "But let those who boast boast in this, that they understand and know me, that I am the Lord; I act with steadfast love, justice, and ighteousness in the earth, for in these things I delight, says the Lord."
Paul, like Jeremiah before him, is cautioning us to get over ourselves and instead to exhibit some care and concern for others. We've heard about it from the prophets. We've heard about it from Christ. Let's get on with it now.