Solid wood has become a luxury option for a practical reason. It takes careful individual attention to fit it properly. This isn't new. In times past, solid wood would be used for gunstocks because it was more or less the only practical technology. More costly rifles and shotguns had stocks carefully fitted by hand, but even a lot of production rifles with hand-fitted stocks (i.e. pre-64 Model 70) suffered a little inaccuracy just because the barrel channel or the recoil lug fit wasn't always consistent. At some point, aftermarket hand-fitting and glass-bedding became a popular upgrade. When did the Acraglas kits come out? Was that in the 70's? Even up into the 90's, manufacturers were offering their least expensive rifles and shotguns with solid birch stocks and they weren't fit perfectly. "Plasticizing" the stock's barrel channel and recoil lug area continued to be popular because it would often enough turn a budget rifle into one that would shoot as well as rifles that cost two or three times as much. The trend the OP has noticed began a long time ago but the result is that we can now buy an inexpensive Savage, Ruger, Tikka etc. with sub-MOA accuracy in part because the low-cost synthetic stock fits perfectly almost every time and unlike solid wood, it doesn't change over time. There's also no need for hours of labor to glass or epoxy bed it to get an accurate rifle. Classic, solid wood is not "dead," but due in part to increasingly short supplies of good wood, rising costs, and the additional labor needed to make it fit well, solid wood will continue to migrate toward the niche of a luxury option -- and it is not the only luxury option because many people will rather spend more on lowering weight with advanced composites, on more sophisticated adjustability, or without compromising extreme accuracy -- for all of which options other than wood are better.
FWIW, all my long guns have beautiful walnut, but if I was buying for some practical reason, I wouldn't dismiss composite stocks at all. Composite stocks are very practical. Wood is not even necessarily impractical but even so, practical is not a requirement for an awful lot of firearms.
