That's a very mistaken assertion. The attribution of the Gospels to two of the Twelve Apostles (Matthew and John) stems from a tradition of the Church that the Gospels came from authentic, eye-witness sources who accompanied Jesus for the 2 1/2 years of His pulic ministry, and especially, from those who witnessed his post-Resurrection glory: t from the very Apostles to whom Christ gave such glorious privileges sand promises. It has an impact on whether we think they are genuine or spurious; whether we think the Apostolic tradition is authoritative, or it is not. It was, after all, only a couple of centuries after that that the 27 books of the New Testament were collected from hither and thither, and recognized as a unified Canon of sacred writings.
And two Gospels are attributed -- again, not by stated authorship in the text, but by Church tradition --- to two of the Apostles' disciples. Mark is secretary-disciple for Peter; and as for Luke, it's only according to a Church tradition dating from the 2nd century that the Luke named as a companion of Paul in three of the letters attributed to Paul himself, was the same man who was the author of Luke-Acts.
The impact of this on belief cannot be overstated. If the early Church hadn't believed that these books came from eyewitnesses and their first-generation disciples, the books would not have been accepted into the Canon.
“The impact of this on belief cannot be overstated. If the early Church hadn’t believed that these books came from eyewitnesses and their first-generation disciples, the books would not have been accepted into the Canon.”
In studying the decision-making process of the canon - originally and subsequently through many iterations - ascribed authorship that was believable counted for a lot. It was not everything Mrs. Don-o. There are books without certainty of authorship - Hebrews comes to mind. There are things Apostles wrote that were not inspired and not included.
I commend to you the study of the canon process. As with much of our history, it is messy. God worked through it. Some errors crept in anyway and were corrected later.
For those reasons, when you read one of the four gospels today, you do not have to believe the authorship. Nor is it necessary to believe it for the words to be true.