I am one of these people, and I think I can help you understand why. Your distinction between buyers and sellers is something that simply does not exist. Everyone is a buyer, or what economists usually call consumers. Everyone produces and becomes a seller in order to consume more. Acquiring gil or money is not an end, it is only a means to an end - consumption. The real value of your currency is determined by the amount of things you can consume with it. If you want prices to be higher so you can acquire more gil, then, undoubtedly, you will not be able to buy much more with the extra gil you are acquiring through production. By working to increase profits of the producers, you invariably reduce the worth of the gil you earn and your real wealth.
These 7-8 crafters role in the economy is to fulfill a need or want of the consumers. Excess supply means that consumers, willing and able to buy the items at that price, no longer need or want that item. Simply producing more at the same price and expecting profit is absurd. The only way to sell those items is to create more demand or reach more people that need or want it, but are unable to purchase at that price. The only thing the producer of the item can do is lower the price to reach a broader market. Only the developers can create more demand for the items by altering systems in the game itself, such as implementing the materia system.
Another key concept is competition. Because you are not the only producer in the market, you must operate simultaneously with others. When supply exceeds demand, each individual producer makes a decision of the value of their labor and will decide accordingly to either lower their prices, shift production, or drop out of the market.
Typically the more effecient producers retain their profits at lower prices; and, because they are more effecient, they are rewarded with the business of consumers. In doing so, the economy is capable of having the most effecient production and providing the most goods and services at the lowest price.
Where you see stagnation, I see satisfaction. Try to imagine the FFXIV market as if it were real life. Everyone's needs or wants are essentially satisfied for the large part, so the only work to be done is in satisfying the needs of a very small sector of the market. If this were real life, we would all be happy and free to do whatever we wanted every day.
That said, your attribution of the 'stagnation' being caused by the pricing system is not entirely accurate either. Causes in economics are typically VERY basic and always being limited to just a few things. When you step away from these very basic causes, you lose sight of the whole thing.
What's causing the current state of the economy is LACK OF DEMAND. There are no consumers who want the goods and services that are available. And there are many different reasons and solutions for this, but addressing the price system is not one of them.