1 Corinthians 1:26-31? Study it out.
The only reason any are saved is because God predestined and elected to save whom he wills, Romans 8:26ff, Ephesians 1 &c; Romans 9. Since you've claimed the classic "anti evangelistic" accusation you may want to read and study how Paul the Calvinist saw and was confident in evangelization because God has his people, the elect, out there whom he will save; Acts 18:9-10; 2 Timothy 2:8-10.
Why you are filled with half-truths? In 1 Corinthians 1 why left the very important context following verses 18-21. Scripture of truth will not fail. Paul's preaching of the cross is not based on worldly wisdom. his main purpose of preaching the gospel is 'to save them that believe' and this will harmonize with Romans 1:16 that the power of God unto salvation is the preaching of the gospel of Christ 'to every one that believeth'. So it takes to believe or not to believe. At the same time, Paul says in v2 that the Corinth believers are sanctified called to be saints
with all that in every place call upon the name of the Lord. Paul in the book of Romans 10: 9-13 correlates this passage. It speaks about
"whosoever" shall call upon the name of the Lord. And the rest of mention scriptures can be explained according to its context as usual.
1 Corinthians 1:18-21 King James Version (KJV)
18 For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.
19 For it is written, I will destroy the wisdom of the wise, and will bring to nothing the understanding of the prudent.
20 Where is the wise? where is the scribe? where is the disputer of this world? hath not God made foolish the wisdom of this world?
21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of
preaching to save them that believe.
Romans 1:16 King James Version (KJV)
16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation
to every one that believeth; to the Jew first, and also to the Greek.
1 Corinthians 1:2 King James Version (KJV)
2 Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints,
with all that in every place call upon the name of Jesus Christ our Lord, both their's and our's:
omans 10:8-13 King James Version (KJV)
8 But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
10
For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
11
For the scripture saith, Whosoever believeth on him shall not be ashamed.
12 For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
13
For whosoever shall call upon the name of the Lord shall be saved.