"Most modern scholars believe..."
That phrase is usually the first part of some a*** compulsive "analysis" of Biblical texts to discern who the "real" authors are, and the one that infuriates me the most is the theory that the works of John the Apostle are by three different Johns, due to differences in "writing style" etc. That is so sophomoric an analysis that it really beggars even a reply.
All of the Biblical works attributed to John were written by the one and only John the Apostle, who did indeed live to a very long age, just as Jesus prophesied. Thus anyone with any knowledge of people realizes that one's style and word usage varies over the decades, according to the purpose of the document, and also to the degree that the author is actively inspired by the Holy Spirit while in the writing. Also, successors will often edit sections to make them more readable.
Revelation reads so differently than the Gospel and the Letters of John because obviously it is the result of complete guidance by the Holy Spirit. I've mentioned this before but will repeat that the scroll that St. John swallowed is the "means" by which he then recalled and wrote the complete telling of the Book of Revelation. That is obviously a different set of circumstances than when he wrote the Gospel of St. John, which serves a separate purpose, and the Letters of St. John, again, different purposes. You cannot mistake, however, the style in all of them, not the "grammar" but the level of spirituality. The Gospel of St. John has the same tone as the Book of Revelation. There are no mysterious "other" "Johns."
*special place in hell for certain 'modern scholars'*
No one should claim to be a Biblical scholar if they are approaching the material with a stance of "agnostic faith," as in, "prove it to me using modern criteria." That is so annoying and is just another attempt to erode the faith.
*rant over (for now!)*