Do you ever do a Google Search? The search engine will bring you immediately to Wikipedia. Some persons automatically assume that everything found there is true, but essentially it is a people’s encyclopedia where anyone who “believes” they understand the topic can write and/or edit the entry in some form. Some writers are experts and some are not. The result is that you can receive misinformation rather than truth. The creators of Wikipedia understand, however, that allowing clearly inaccurate or erroneous information will nullify the integrity of their site; so they encourage the removal of that which is just not true or sufficiently inaccurate to be misleading for someone.
Not everything that is written or published is true, even though some people prefer to believe it or wish it were true. The Early Church understood that they had to be discerning about what was included in the Canon (which is what they called the Bible). Here is a definition of that found in a reliable on-line dictionary:
“The collection of books received as genuine Holy Scriptures, called the sacred canon, or general rule of moral and religious duty, given by inspiration; the Bible; also, any one of the canonical Scriptures.”
It was because they were concerned with the integrity of truth that they exercised some judgment in the matter of what to include. The Gospel of Mary was never in the Bible and therefore was not “cut out.” It simply did not rise to the high standard for inclusion.
The Canon was actually developed over a period of several centuries, not a one time, once and done meeting.
One of the most significant of those meetings was the Council of Carthage in 397 AD.
Now as to the Gospel of Mary itself, you should note that the this would probably not even be on the table for discussion if it were not for a fiction writer, Dan Brown and a work of fiction called THE DAVINCI CODE. The words Brown puts into the mouth of scholars would not have been spoken by most reputable historian and scholars. Read more … Mention of this “gospel” does not appear until the third or fourth century when the four Gospels–Matthew, Mark, Luke and John were already several hundred years old and in wide use in churches. The mention of the “gospel of Mary” actually also comes a later work that was also written 200 years after the Four Gospels.
In Nag Hammadi there is a fragment of this gospel which clearly shows it to be of gnostic not apostolic origin and it is very incomplete at best, containing ideas that were not current with the gospels presented by the direct followers of Jesus.