is a Visual Novel and as such uses none of RPG Maker's core functionality.
Sorry, but it does.
a. It uses the map editor to generate the visual areas the player travels through and interacts with others in. I understand some players may not like this, but maybe the developer does and achieving the same effect within DAZ Studio would of required a lot more effort.
b. It uses the event editor to control when activities occur, and what happens during those activities.
It can easily be made in Ren'Py, cleaner and simpler.
While this may be true, that would also require the developer to learn how to program in Python and how to use the Ren'py Framework, and both of those activities are harder for a non-programmer than learning how to use RPGMaker's point and click interface.
If I'm not mistaken some guy did just that a few weeks ago.
To be more precise, that programmer created a custom tool that can convert a (this) RPGMaker based game into a Ren'py based one. They then uploaded the Ren'py based game here, along with an explanation of why a number of scenes don't include a background image due to the fact that the original developer of the game hadn't generated such images because they were relying on RPGMaker to do that for them.
I understand that some people don't like playing RPG like games and the reasons they may feel that way, what I don't understand is the recent insistence by (some of) those people that these games be made using only Ren'py. Surely there are enough games being produced that there is enough room for developers to use whatever engine they either prefer or feel more comfortable using.