The general goal of a decompilation is to convert machine code back into something that, when compiled, generates machine code that is similar to or identical to the original machine code. But most decompilation projects also aim to make sure that the decompiled code is actually workable by humans so as to preserve, port, extend and generally make a codebase that has clear intent and may be similar to the code used to write the original game.

Ai decompilations are often done such that they technically check the first box, but are completely unusable for a normal engineer to want to use due to insane verbosity or in some cases just getting context or intent entirely wrong. Without proper guidance, the codebase is basically just an incoherent mess. With deep guidance, it would still take ages for these projects to be decompiled. For reference of how long they take and how thorough a proper decompilation can be check out the jak 1 decompilation project.