The thesis of the article is middle class stagnation (the actual truth is, inflation-adjusted hourly wages have fallen since the early 1970s, they have not stagnated). These "increased benefits" are due to skyrocketing health costs which the employer has been paying, not any new fringe benefits. Because employers in the US have been fighting universal healthcare for decades, unlike every other industrialized country. They fight tooth and nail to stop universal health care with campaign donations, then cry how much they have to pay into the HMOs of their workers.
A worker who purchases the same basket of goods and services that the typical family has in 1970 is not going to "cut it". To make the same wage he did in 1970, he will now have to pay for his own job training, college degree and so forth. Employers now require more education from workers. The typical family is now forced to pay a new expense in their basket - their own training and educational costs - forced meaning if they want to remain a typical family, and not fall further then they already have.