Is it the Word of God, or not? John 1 might help you understand the point I'm making. The Word of God has been around literally forever.
The fact that God makes much of "The Church" is important, no doubt, and The Church has a huge responsibility, but it is has no authority over conscience. Nor does it have the authority to forgive sins. So it is no firm foundation. No anchor.
Your logic, that something-come-lately is not as reliable, or has no particular authority, compared to what has been around a long time, is as fallacious as the notion that larger numbers of attendees makes a thing more valid, or that a belief more rabidly pursued is more valid, or that
But what is remarkable to me here, though not surprising, is the notion that "The Church" is, somehow, the RCC, with all its hierarchy, pope adoration, saint worship, etc. and not the notion that it is the redeemed elect, wherever they are.
Take a look at Acts 8:26-40, and explain how this fits into your narrative