Part of the problem is that you can't write a 20 page manual that will turn a machinist into a computer geek any more than you can write a 20 page manual that will turn a computer geek into a machinist. Each has years of experience to draw on.
Configuring things to work with Mach3 requires a breadth of knowledge you have to know some about machining, electronics, computers, software etc., etc., and you can't distill all of this into a small manual and cover every situation. Just getting an Ethernet device to work can be a challenge as there are so many variables: does your companies PC policy prevent you from making the needed changes on the PC, is the firewall or AV program your using going to interfere, does your network adapter require a cross over cable or not, does your PC have some sort of other software on it that will cause problems? Not to mention that folks start this journey at all different places, some folks struggle to turn the PC or unzip a file and others are a whiz.
I know it is frustrating when your just trying to make something work and I'm certain there are things that can be done to improve manuals and set up procedures. I'm also certain that no matter what sort of manual gets written it will never cover every scenario or makes sense to every reader.