Some books of NT scripture, such as the Didache, were eventually declared apocryphal and excluded from the canon. Who had authority to do this if not the Catholic Church. Was the Didache unjustly excluded?
If you could bring yourself to admit that what you keep referring to as the "Catholic Church" was, in reality, all the local assemblies of believers in Jesus Christ who followed the orthodox teachings they received either directly from Jesus Christ or his hand-selected Apostles and disciples, then we may agree on this point. As the article from Warfield expressed:
The Canon of the New Testament was completed when the last authoritative book was given to any church by the apostles, and that was when John wrote the Apocalypse, about A.D. 98. Whether the church of Ephesus, however, had a completed Canon when it received the Apocalypse, or not, would depend on whether there was any epistle, say that of Jude, which had not yet reached it with authenticating proof of its apostolicity. There is room for historical investigation here. Certainly the whole Canon was not universally received by the churches till somewhat later. The Latin church of the second and third centuries did not quite know what to do with the Epistle to the Hebrews. The Syrian churches for some centuries may have lacked the lesser of the Catholic Epistles and Revelation. But from the time of Irenæus down, the church at large had the whole Canon as we now possess it. And though a section of the church may not yet have been satisfied of the apostolicity of a certain book or of certain books; and though afterwards doubts may have arisen in sections of the church as to the apostolicity of certain books (as e. g. of Revelation): yet in no case was it more than a respectable minority of the church which was slow in receiving, or which came afterward to doubt, the credentials of any of the books that then as now constituted the Canon of the New Testament accepted by the church at large. And in every case the principle on which a book was accepted, or doubts against it laid aside, was the historical tradition of apostolicity.
Let it, however, be clearly understood that it was not exactly apostolic authorship which in the estimation of the earliest churches, constituted a book a portion of the “canon.” Apostolic authorship was, indeed, early confounded with canonicity. It was doubt as to the apostolic authorship of Hebrews, in the West, and of James and Jude, apparently, which underlay the slowness of the inclusion of these books in the “canon” of certain churches. But from the beginning it was not so. The principle of canonicity was not apostolic authorship, but imposition by the apostles as “law.” Hence Tertullian’s name for the “canon” is “instrumentum”; and he speaks of the Old and New Instrument as we would of the Old and New Testament. That the apostles so imposed the Old Testament on the churches which they founded — as their “Instrument,” or “Law,” or “Canon” — can be denied by none. And in imposing new books on the same churches, by the same apostolical authority, they did not confine themselves to books of their own composition. It is the Gospel according to Luke, a man who was not an apostle, which Paul parallels in I Tim. v. 18 with Deuteronomy as equally “Scripture” with it in the first extant quotation of a New Testament book of as Scripture. The Gospels which constituted the first division of the New Books, — of “The Gospel and the Apostles,” — Justin tells us, were “written by the apostles and their companions.” The authority of the apostles, as by divine appointment founders of the church, was embodied in whatever books they imposed on the church as law, not merely in those they themselves had written.
The early churches, in short, received, as we receive, into their New Testament all the books historically evinced to them as given by the apostles to the churches as their code of law; and we must not mistake the historical evidences of the slow circulation and authentication of these books over the widely-extended church, for evidence of slowness of “canonization” of books by the authority or the taste of the church itself. (http://www.the-highway.com/ntcanon_Warfield.html