"Do not deceive yourselves. If any one of you thinks he is wise by the standards of this age, he should become a "fool" so that he may become wise. For the wisdom of this world is foolishness in God's sight. As it is written: 'He catches the wise in their craftiness', and again, 'The Lord knows that the thoughts of the wise are futile.'" NIV translation
This inferior building that Paul has been talking about is based on human wisdom and understanding. Even today, you have many who think they are so wise and will try to build faith on some obscure teaching instead of on the grace of God through Jesus Christ. You have all kinds of people chasing this earthly wisdom with all kinds of college degrees (even Bible college degrees) and in the process they forget that wisdom comes from God through the Holy Spirit and not by man. Those who simply focus on the Word of God are commonly called "fools" or "holy rollers" or some other name but, as Paul says here, we should become "fools" so that we can have the wisdom that is from God.
"So then, no more boasting about men! All things are yours whether Paul or Apollos or Cephas or the world or life or death or the present or the future - all are yours, and you are of Christ, and Christ is of God." NIV translation
This passage speaks of true unity in the faith and the fact that what matters is our relationship with God through Jesus Christ. We have all things because He is the owner of all things and we are His heirs. Our relationship with him is our greatest reward but He also throws in other things because of His love for us.