If it wasn't for the Writings of the fake Apostles (since the Gospels were not written by real Apostles), there would be no Jesus Christ and no Christians today. So it is only because of the false attributes of glory and miracles, imposed on the ordinary, average, prophet known as Jesus of Somewhere (not Nazareth) that Christianity was created.
If the one referred to as being Jesus actually had his real life story recorded on Video and an autobiography written from his own memories, he'd likely be now regarded as just another Charles Manson.
If the apostles and prophets weren't such a big part of Christianity, why focus on their writings in the Bible? If you take out the prophets and apostles, all we have left to go on are the four Gospels and the Torah. The Bible goes from dozens of books to just nine if we stop believing in the works of the prophets and apostles. The difficulty is accept modern-day prophets who are just as valid as ones from 2,000 years ago when the Holy Spirit moves through them. When modern-day prophets try to spread their message, they are called "cultists" instead of "real" prophets. There is a difference between a cult and a prophet.
I believe that the apostles and the prophets are both a vital part of Christianity. I think some organization tend to concentrate on the New Testament, but overall I think it would be difficult to remove anything found in the Bible and still refer to it as Christianity. All parts are important or it is not a whole.
Jesus the rabbi was a compelling figure in history, but at his death his work and name might have disappeared if it were not for his apostles and disciples, especially Paul. These people went out into the world telling the story in oral tradition that was eventually written to become the Gospels.
Yes, the Apostles and Prophets are a vital part of Christianity, because they are a vital part of God's message. Part of the reason that we know God is real is that prophets proclaimed his coming. The Apostles set the example for us of how to show God's message until he returns.
The only necessary part of Christianity is that followers believe Jesus Christ is their lord and savior. It is not necessary for Christians to believe in the Apostles or the Prophets . There are many different scriptures about Jesus, and most of them do not agree. The only important part of the religion is Jesus.