The idea of a disposable firearm has a certain degree of merit for military purposes. One of the factors with military small arms, as well as other equipment, is the possibility of loss or destruction in action, something which tends to inhibit the issue of expensive weapons. But trends can be confusing.
In WWII, some innovative designs were introduced, some of which continue to influence firearms today. The M3 submachine gun and the Sten gun were both innovative in the way they were manufactured, but submachine guns are not what they used to be, in a manner of speaking, because of the real innovation of the so-called assault rifle. That first appeared in Germany as the MP-44. Not only was the cartridge innovative but so was the production of the rifle, which by the way was no lightweight. From what I've read it was not an expensive thing to manufacture, nor did it look like it, assuming the existence of sufficient stamping equipment in the shop. It is true that some relatively inexpensive firearms require some sophisticated heavy-duty equipment but they can be turned out quickly. So anyway, everyone thought the infantry gun of the future would be just stamped sheet metal. Some were. But the AK-47 certainly wasn't. Later ones were, however, so the theory does hold some water. Nowadays, more plastic is used than ever before but production of a firearms-quality plastic part is not all that simple but probably close to the production capability required by a stamped part (only different).
Innovation is not the same thing as novel but hopefully, it means something better.
