The church being built is the only church comprised only of believers who believe the essential faith peter confessed, these being "living stones," which make up the body of Christ, the "household of faith," which Christs feeds and leads, and which transcends the different organic ecclesiastical communions in which they operate.
And their basic unity of the Spirit is based on a shared conversion and relationship with the Lord Jesus, and thus they preach Him, not their particular church. A mark of a false, cultic "church" is that they incessantly exalt and promote the latter.
It seems rather clear that the RCC is indeed a cult.