You don't find it curious that all forms of Christianity that predate Protestantism more resemble Catholicism in both doctrine and practice? Maybe I'm wrong and the Orthodox Church is the true Church. But even in that case my error is being on the wrong side of a schism rather than having an incorrect faith. We know what the early Christians believed because we have their writings. Either they were in error or Protestantism is an sixteenth century innovation with no substantive ties to historical Christianity as it stood the the first fifteen hundred years.
The Church defines what it claims has always been believed.
Over time as challenges to the faith emerge, counsels are called to articulate the faith via dogmatic action. Vatican I no more invented papal infallibility than Nicaea invented the divinity of Christ. The faith has already been revealed. But not all of it has been dogmatically articulated.