It's not too hard, it's just a matter of knowing how to do it. If you don't know how to do it (majority of people), then it's "impossible". And you don't have to be massively intelligent, you just need some experience. Blizz-ABS wasn't made by a genius either and neither was RMXP and neither was Windows. The two latter were actually made by not just one person. -_-
You can say the same for the audio module rewrite. The basic is a custom audio API for Windows made by somebody completely else. All the scripter did was created a so-called bridge between the DLL methods and functions and RMXP. You don't have to be a genius for that. Just knowing how to call DLL functions from RMXP is pretty much the only knowledge you need along with the knowledge how the audio calls were made.
The rotating Mode 7 is a different story. If I am not wrong, the DLL was created by the scripter. But yet again, the basic knowledge you need is how 3D rendering works. Neo Mode 7 still lags on my PC, there's probably no work around that. It's running at around 20 fps when I have both CPU cores at 1.2GHz. Note that I am talking about a non-rotated view.
Don't get me wrong, I'm not turning down those works. Somebody with the knowledge to even make them probably has enough understand that he made them the way they should have been made. In any case those script are great additions to the RM community. I am considering of using both the custom audio module and the rotating Mode 7 in my own game. The former will be most probably there and the latter only if the lag is low enough when I combine the script with my world map slicer and my other anti-lag systems.