There are many reasons why the International Commission on Zoological Nomenclature (ICZN) is in trouble, but fundamentally I think it's because of situation illustrated by following diagram.
Based on an analysis of the Index of Organism Names (ION) database that I'm currently working on, there are around 3.8 million animal names (I define "animal" loosely, the ICZN covers a number of eukaryote groups), of which around 1.5 million are "original combinations", that is, the name as originally published. The other 2 million plus names are synonyms, spelling variations, etc.
Of these 3.8 million names the ICZN itself can say very little. It has placed some 12,600 names (around 0.3% of the total) on its Official Lists and Indexes (which is where it records decisions on nomenclature), and its new register of names, ZooBank, has less than 100,000 names (i.e., less than 3% of all animal names).
The ICZN doesn't have a comprehensive database of animal names, so it can't answer the most basic questions one might have about names (e.g., "is this a name?", "can I use this name, or has somebody already used it?", "what other names have people used for this taxon?", "where was this name originally published?", "can I see the original description?", "who first said these two names are synonyms?", and so on). The ICZN has no answer to these questions. In the absence of these services, it is reduced to making decisions about a tiny fraction of the names that are in use (and there is no database of these decisions). It is no wonder that it is in such trouble.