Nobody is denying that Paul had revelations directly from God. But he also deferred to the authority of the apostles on some matters. The two are not mutually exclusive.
Here's an example in this passage from Acts. Since I'm always told by our Protestant brethren that Scripture is easily understood, there shouldn't be a problem here.
And some coming down from Judea, taught the brethren: That except you be circumcised after the manner of Moses, you cannot be saved. And when Paul and Barnabas had no small contest with them, they determined that Paul and Barnabas, and certain others of the other side, should go up to the apostles and priests to Jerusalem about this question. They therefore being brought on their way by the church, passed through Phenice, and Samaria, relating the conversion of the Gentiles; and they caused great joy to all the brethren. And when they were come to Jerusalem, they were received by the church, and by the apostles and ancients, declaring how great things God had done with them. But there arose some of the sect of the Pharisees that believed, saying: They must be circumcised, and be commanded to observe the law of Moses.
And the apostles and ancients assembled to consider of this matter. And when there had been much disputing, Peter, rising up, said to them: Men, brethren, you know, that in former days God made choice among us, that by my mouth the Gentiles should hear the word of the gospel, and believe.
Acts 15: 1-7
Did you get that? Paul and Barnabas became embroiled in a dispute with some from Judea over the question of circumcision. The resolution to this dispute came not via direct revelation from God, but through the elders in Jerusalem, in particular, St. Peter.
In the years before the New Testament appeared, the Church was not paralyzed. On the contrary, it went about its business, commissioning evangelists, teachers, priests, deacons and resolving disputes without reference to a book.
As the above passage from Acts makes perfectly clear, in the early Church, authority was human and not written.
Where did Peter get his information in order to confer with Paul and Barnabas? Acts, Chapter 10. By DIRECT REVELATION IN A VISION FROM CHRIST. And BTW, Paul was saved in Acts, Chapter 9. So he ALREADY had revelations from the risen Christ. This is how Peter knew that Paul’s authority was from God. And this is how Paul was able to withstand Peter to his face (Gal. 2:11). REVELATIONS FROM THE RISEN CHRIST. NOT some written source.
I think you left out the word 'other' in front of Apostles. I don't think Paul deferred to the 'authority' of the other Apostles as much as he concurred that their viewpoint on 'some matters' were in consonance with the revelation he had received from Christ.