ORIGINAL: ernieschwitz
As a modder, and someone who was offered a chance to make a game, once, I think I can explain what the first thought that goes through a creator of any mod or game is: Do I want to do it?
Much like players get a kick out of playing something that they love, a game designer also has feelings about the things they do. There has to be a drive. I think this drive will supersede any other thought to begin with. Then perhaps that person will look into, what can I do here that is unique, but also serves the subject well. Nobody wants to copy something that is already out there.
You can say all you want to a designer of games what you want. It won't change the way they feel about a subject. For instance, I feel that wargames made after the advent of the atomic bomb are impractical, and to me feel "funny" (in a bad sense) because the players always have the option of breaking the emergency glass (firing those nukes, and getting retaliated at) and then the game ends in a tie. That is just how I feel.
In the same way I don't want to make a game from a time before tanks (and with guns). My reasoning for this is that I don't see the joy in playing and thus making a game that will be static warfare, with very little chance of breakthroughs and rapid movement. That is just how I see these periods.
These views may be wrong or right, but it doesn't change my joy of doing one rather than another.
Often what a game maker, will need is a vision. A reason to do something. This will drive creativity much more than trying to sit down and solve the squaring of the circle, by inspiration (which is what it is to demand that games be innovative).
Anyway, those are my 3/4s of a crown.
It appears that you do not understand the power and maneuverability of concentrated horse cavalry. Nor what the various types did. Nor the shock and awe of elephants . . .