I agree with John MacArthur on Laodicea, they were a church in name only and Christ was offering salvation, particularly with His "buy from Me's"You are correct when you say that the passage is directed at churches -- which are made up of regenerated persons. Therefore, you miss the point of the passage when you use it as a proof text for evangelism. Christ is contending with those already evangelized, not the lost, when He says that He would like to come in! He made a point of the church at Laodicea that they, though calling themselves a "church," did not let even their Master and Savior into their midst.
If anything, this passage describes churches (loosely used) like Joel Olsteen, T.D. Jakes, etc., or worse, cults like Mormons or Jehovah's Witnesses, who are heretical or close to it in their doctrines and practice, yet say that they represent Christ. It is not an evangelism passage, but it has been used that way by so many for so long, that it is now one of the go-to passages.
Think Westoboro Baptist Church.