This is a common. Roman polemic against scripture that has been used time and again even though it is factually false. First, there was not a large gap between the events of the NT and the writing of the contents there of. The first christians were Jews who used the Hebrew Old Testament as scripture. The first christians outside of Judea would have used the Greek translation of the OT called the Septuagint, or the LXX since this was the common language of the eastern Roman Empire. The LXX and the Apostle's preaching and teaching would have made up the Rule of Faith. This teaching was handed down (παράδοσις) to the various churches that the apostles founded. These teachings were later written down in the middle of the first century.
The first book of the New Testament was probably Galatians in the 40's AD. We know that Paul's letters were circulated among the various churches from Col 4. The synoptic Gospels were likely written in the 50's ad, with John being later in the early 60's AD. The last book to be written was probably Revelation prior to 70 AD. That means if Christ ascended into heaven in 33AD then the first writings may have been as little as 7 years later. If the findings in Qumran are valid, the fragments of Mark, Romans, 1 Timothy, 2 Peter and James were found as part of the Dead Sea Scrolls. These date between 50-80AD which is extremely early. That means that these documents were already circulating before the close of the first century and probably during the middle part too. Add to that the finding of early papyri such as p52 which dates from the early 2nd century. Oddly enough p52 is from a codex meaning someone bound this in book form with other writings (presumably other books of scripture).
Then you have citations of the NT from the early church fathers such as Clement of Rome in the late first century, Ignatius of Antioch in the early 2nd century. By the mid to late second century you have Justin Martyr, Irenaeus, Clement of Alexandria, Tertullian and so forth.
So to the charge there was no bible as we know it until a much later date. Yes, but to say that is misleading. The fact is there were collections of NT scriptures in the possession of people very early on and they were treated as authoritative.
As to the contents of the New Testament there was a pretty clear consensus right away with the majority of 27 books we now recognize as canonical. The gnostic texts were never really considered as they were clearly a different character and frankly of a different religion. The disputes that regarding the canon were really around a few books, such as 2 and 3 John, 2 Peter, Hebrews, James, Jude and Revelation. Other texts that were considered by some as canonical were the Apocalypse of Peter, Shepard of Hermas, the Epistle of Barnabas and the Didache.
Eusebius, the ancient church historian observes regarding the rejected texts:
And further, the character of the style is at variance with apostolic usage, and both the thoughts and the purpose of the things that are related in them are so completely out of accord with true orthodoxy that they clearly show themselves to be the fictions of heretics. Wherefore they are not to be placed even among the rejected writings, but are all of them to be cast aside as absurd and impious.
Eusebius of Caesaria. (1890).
The Church History of Eusebius. In P. Schaff & H. Wace (Eds.), & A. C. McGiffert (Trans.),
Eusebius: Church History, Life of Constantine the Great, and Oration in Praise of Constantine (Vol. 1, p. 157). Christian Literature Company.
The reality was the NT canon was largely decided by the mid to late second century. Athanasius the Great gives us his list of the NT books we have today in 367 AD. How did he come up with this list? Thankfully for us he told us in the text of his letter:
In proceeding to make mention of these things, I shall adopt, to commend my undertaking, the pattern of Luke the Evangelist, saying, Forasmuch as some have taken in hand,* to reduce into order for themselves the books termed apocryphal, and to mix them up with the divinely inspired Scripture, concerning which we have been fully persuaded, as they who from the beginning were eye-witnesses and ministers of the Word, delivered to the fathers; it hath seemed good to me also, having been urged thereto by the brethren, and having learned from the beginning, to bring before you the books included in the Canon, and handed down, and accredited as Divine; to the end that any one who has fallen into error may correct those who have led him astray; and that he who continues stedfast in purity, may again rejoice, having these things brought to his remembrance.
Athanasius of Alexandria. (1854).
The Festal Epistles of S. Athanasius (H. Burgess, Trans.; pp. 137–138). John Henry Parker; F. and J. Rivington.
Athanasius is pointing to the fact that the canon was already clearly delineated from false writings that is plain to him. Meaning he didn't make up the canonical list he is rather reproducing it.
So when did Rome officially declare what the canon was? April of 1546 at a session of the Council of Trent. I am not suggesting that Rome didn't know what the canon was until the sixteenth century but I am pointing it out to illustrate the absurdity of this "Table of Contents" argument.