The church is the body of Christ not a physical building or organization of man
As the Nicene Creed tells us, the Church is one, holy, catholic, and apostolic.
Yes, the church is the People of God, but also catholic (which means universal) organization founded on the apostles.
Jesus said his Church would be "the light of the world." He then noted that "a city set on a hill cannot be hid" (Matt. 5:14). This means his Church is a visible organization. It must have characteristics that clearly identify it and that distinguish it from other churches. Jesus promised, "I will build my Church and the gates of hell will not prevail against it" (Matt. 16:18). This means that his Church will never be destroyed and will never fall away from him. His Church will survive until his return.
Among the Christian churches, only the Catholic Church has existed since the time of Jesus.
Apostolic succession continued through the ordination of presbyters (priests) and bishops. Titus 1:5-9 *For this reason I left you in Crete so that you might set right what remains to be done and appoint presbyters in every town, as I directed you, on condition that a man be blameless, married only once, with believing children who are not accused of licentiousness or rebellious. For a bishop as God’s steward must be blameless, not arrogant, not irritable, not a drunkard, not aggressive, not greedy for sordid gain, but hospitable, a lover of goodness, temperate, just, holy, and self-controlled, holding fast to the true message as taught so that he will be able both to exhort with sound doctrine and to refute opponents.
The Apostles replaced Judas as an apostle.
Acts 1:20, 26 "For it is written in the book of Psalms, Let his habitation be desolate, and let no man dwell therein: and his bishoprick let another take....26 And they gave forth their lots; and the lot fell upon Matthias; and he was numbered with the eleven apostles."(KJV)
The Epistle of Ignatius to the Smyrnaeans Chapter 8 says. "See that you all follow the bishop, even as Jesus Christ does the Father, and the presbytery as you would the apostles; and reverence the deacons, as being the institution of God. Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is [administered] either by the bishop, or by one to whom he has entrusted it. Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever Jesus Christ is, there is the Catholic Church. It is not lawful without the bishop either to baptize or to celebrate a love-feast; but whatsoever he shall approve of, that is also pleasing to God, so that everything that is done may be secure and valid."