They actually aren't. Median income is measured as a median for a reason. Poverty line statistics are taken at the low end. Local CPI and price data is taken and reported. And all of those numbers are, indeed, getting better and not worse.
I repeat this everywhere this subject comes up, but the real reason things look like they're getting worse is unsavory. More than two generations back, people were on balance poorer but they were black, so they didn't matter. Or they were immigrant, or single mothers, or institutionalized, or otherwise invisible to the white-picket-fence set who were all buying their family homes on one income.
Well, all those other demographics have done super well in the last half century, reaching parity with white men at the low end of the spectrum.
And those white men are the pissed off groypers detailed in the article. Not "Americans" in the abstract.
I mean, it's true they can't afford homes easily! Neither could minorities in the sixties, but we don't talk about that part.