Moreover, who said that Jesus had to specifically tell His disciples to write Scripture? Why does that even matter? If we were not supposed to have the New Testament, then it would simply not exist. Interestingly, Jesus did command the Apostle John to write down His teachings:
Those same apostles whom Christ had commissioned to preach the gospel knew that their writings were divinely inspired and thus to be considered inherently authoritative:
"If anyone thinks that he is a prophet, or spiritual, he should acknowledge that the things I am writing to you are a command of the Lord." (1 Corinthians 14:37)
"If anyone does not obey what we say in this letter, take note of that person, and have nothing to do with him, that he may be ashamed." (2 Thessalonians 3:14)
"how the mystery was made known to me by revelation, as I have written briefly. When you read this, you can perceive my insight into the mystery of Christ, which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit." (Ephesians 3:3-5)
"and regard the patience of our Lord as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you, as also in all his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the Scriptures, to their own destruction." (2 Peter 3:15-16)
One may ask, "Why would Jesus Christ not want His teaching to be written down as Scripture?" The upcoming production of the New Testament was implied by Him saying that the Holy Spirit would lead the twelve disciples to all truth (John 16:13). Scripture was produced as the apostles died off and the Lord's return seemed distant.
The Roman Catholic Church is chiefly focused on proclaiming the authority of its own papal office to the world. That is something which Jesus Christ never instructed the apostles to do. He never once said anything about an infallible interpreter of Scripture.