I think people are naturally more careful about what they write when they need to put their name to it.
The reason Watchtower publications became anonymous upon the death of president Rutherford is purportedly because the new president Knorr didn't write Watchtower material and didn't want this to be known, which it would be if someone else's name appeared on the literature.
Fred Franz is credited with authoring a large amount of Watchtower literature including the NWT and many of the prophetical commentaries and doctrinal tracts of the postwar period, such as Babylon the Great Has Fallen and The Word Who is He According to John.
Some have speculated that Franz also wrote the later books attributed to Rutherford. Technical analysis should now/soon be able to settle that question, as well as the authorship of the Studies in the Scriptures. (Maria Russell claimed she wrote them)
Notable books that were not authored by Fred Franz include the Aid/Insight books, the Commentary on James, Happiness, Life How Did it Get Here? Writers included Ed Dunlap, Raymond Franz, Colin Quackenbush and others.
Lloyd Barry and John Barr are credited with some of the writing in the 1980s and 1990s.
Who took over from them is a bit of a mystery. Among current GB members, Jackson, Sanderson and Splane appear to be the most likely candidates for involvement in the revised NWT and other projects. But GB members perhaps have little time for writing.
Plus Watchtower doesn't actually publish much new material now anyway, do they? Maybe they don't need many writers any more. Even WT study articles are revisions of earlier articles (the latest "avenger of blood" article a case in point).