Prototypes can be useful without modeling the whole game. For instance, to iterate on battle mechanics it might be sufficient to have a prototype that just models a single battle with one screen, fixed enemies, no AI, you play both the character and the enemy actions, etc.
So my current internal debate is whether to teach myself enough about coding to create a prototype, or ask someone to do it for me. I would love to learn to do it myself, but I already have rather a lot on my plate around my silly full-time job and doing the writing/structure/artwork for the game. At the very least I would like to learn enough about programming so that I can be a good project manager and leader and communicate properly with programmers- hence the reason for my original post.
Again, check out RPG Maker (or equivalent) and just start messing around in it. I haven't used it myself but reportedly it is very friendly to beginners.
Just a spreadsheet program can be enough for some things, like modeling the damage output of a character with given abilities/equipment and the probability of winning against a certain type of enemy.