First of all, that is E.P.C. Second, the word that we render as church is ekklesia. It is a combination of two words, ek, a prepositon meaning out of, and kaleo, meaning called. Literally, "the called out ones".
It is wrong to confuse evangelism, going into the world and preaching the gospel, with the the function of the church. Evangelism is an outreach of the church. The function of the church is as follows:
1)To worship God in Spirit and in Truth;The church is not a place where God's truth is accomodated to the culture. Rather it is a place where God's people come have their lives altered by the truth.
2) To equip it's members though the preaching of the word and right administration of the sacraments, for the purpose of carrying out the great commission;
In respect to the culture and some of it's beliefs, C.S. Lewis once made this observation;
...These things are fiction. They may be usefull fiction, and in some cases neccessary fiction, but they are still fiction. When we come into the presence of God for worship we must leave fiction outside the door.
Paul preached Christ crucified, and the Holy Spirit gave results. In engineering we have this saying: "If it ain't broke, don't fix it!" It seems to me that people maintaining that it needs fixed still have to prove that it's broken. i believe you can trace the decline in the effectiveness of the church in it's outreach to the attempts to "fix what ain't broken". The church hasn't failed, the new methods have, simply because faith has been placed in method rather than the promise of God.
Paul wasn't trying to find common ground with the Athenians. He was trying to knock them out of their frame of reference and get them into God's frame of reference.