The organization of knowledge into distinct branches and categories is a natural outcome of intellectual growth as scholarship accumulated over the centuries. The earliest example was the compilation of the Quran into a single volume during the era of the Rightly Guided Caliphs, followed by the systematic recording of the Prophet's Sunnah in organized collections.
Pioneering scholars such as Makhul (d. 113 AH) and az-Zuhri (d. 124 AH) initiated the formal writing and compilation of hadith. This practice was grounded in the juristic principle of al-masalih al-mursalah (considerations of public welfare), which allows for practices that serve genuine community needs even without explicit textual instruction.
The question of whether this constitutes a "good innovation" depends on how one defines the term. In its strict technical sense — referring to newly invented practices in worship — the Prophet (peace be upon him) stated: "Every innovation is misguidance." Under this definition, categorization cannot be called innovation since it is not a matter of worship.
However, in the broader linguistic sense, many classical scholars including ash-Shafi'i and an-Nawawi distinguished between beneficial and harmful new practices.
The correct understanding is that organizing knowledge, compiling textbooks, and systematizing academic disciplines are not religious innovations at all. Their purpose is to make prescribed Islamic objectives more accessible — they are practical tools, not acts of worship in themselves.