does that mean all churches?
Christ may be found amongst certain churches...but it doesn't mean that the church is the source of salvation. That is reserved for the Solo Savior.
Note, too, in Romans 6:3, we are baptized into a Person, Jesus Christ...not into any church body!
Salvation is through Christ, not a church.
Mormonism teaches that to be truly saved (they call it exaltation), a person must be a member of the Mormon church and do a laundry list of works.
The Church of Christ is universal body of all believers, not just one denomination.
It means, "Not a SPECIFIC church.";
as in,
"Only WE have the CORRECT way to GOD."
28. Then they asked him, "What must we do to do the works God requires?"
29. Jesus answered, "The work of God is this: to believe in the one he has sent."