The title is hyperbolic as is the weak assertion that "broad swaths may no longer have influence..."

Publicly available data show that the middle 40% are responsible for more than one-third of consumption; the labor force is large and strong; and lower income spending is relatively flat over the past ~10 years.

The upper income group is indeed spending more--and that is something to watch carefully with respect to broader market business trends. There may even be opportunities to exploit if the smaller segments are less served.