> Inflation adjusted wages have been relatively flat, not decreasing
Inflation adjusted median household income peaked in 1999, and its current level is below what it was in 1997. [0] Mean household income has done better, because the very good results at the top influence the mean, but have no impact on the median.
Real hourly wages for middle- and low-income workers have been stagnant for decades; over a ~3 decade period dropping slightly for low income workers and gaining slightly for middle-income workers. (And lower for both categories than they were a decade ago.) And real hourly wages for young college graduates are below what they were in the late 1990s.
And, in the same time as wages have dropped, the key non-wage benefit (employer health coverage) has also dropped, with fewer recently-employed young graduates (of high school and college, measured separately) having employer-sponsored insurance than in the past. [1]
> At a macro scale people in the United States aren't getting poorer, they're just not getting relatively richer over time.
No, other than capitalists and a narrow slice of elite workers, they're actually getting poorer.
[0] https://research.stlouisfed.org/fred2/series/MEHOINUSA672N
[1] http://www.epi.org/publication/charting-wage-stagnation/