We have the most people ever, with the smallest percentage ever in extreme hunger. So I’m guessing you don’t mean suffering from starvation. Who is suffering and why are they suffering much much more?
(note that the green line marks the mean gain, at about 25%, not zero)
So the typical 1st-world person sees people on both sides of them gaining by leaps and bounds, while their own situation is stagnant. That is bound to cause some bitterness. The people below are now providing competition that pushes down the cost of labor, both via outsourcing and immigration.
This is a microcosm of the whole world, but the statistics about white, middle-aged suicide increasing so much in the west indicates to me a profound suffering, exactly where the article is claiming middle class people are getting some hidden benefit that makes up for the rich getting richer.
Workers. As more demands are pressured to be met, efforts to crush unions are getting stronger, and wages are not increasing, workers are suffering more than ever.
Not to say that it doesn’t suck out there for some laborers, but suffering more than ever? Pinkerton agents used to shoot up union rallies, and people (often children) used to not uncommonly get their limbs yanked off by machinery.
The problem is the "more than ever" part. Nobody is denying there are problems (and there always will be), but the collective situation is better than it's ever been before.