Yeah; John pointed how well THAT worked out; didn't he!!
Except those who were contemporaries of John were among the early Church fathers who painstaking worked through hundred of manuscripts to separate the false from the true. They worked for hundreds of years always making sure the written word was consistent with the sacred oral tradition. For as John himself wrote Christ said and did many things that were never written down.
So why don’t Protestants go back and assemble your own Bible? And while at it have your own calendar for Christmas and Easter? Or maybe just toss a coin and join anyone of the 30,000 varieties of contradictory Protestant nonsense that is out there?
As a Catholic, I can attend any Catholic Church from here to Timbuktu, and the Mass - the highest form of prayer and worship- is the same. The same goes for Catechism of the Church. One Church, One Truth, for all peoples and all nations, for all times and until the end of time. This explains why hundreds of former Protestant theologians have converted to Catholicism while low-info Christians are drowning in shallow theological waters.