I'm always a little wary of the elitist high/popular culture binary being at play with reports such as this, but its intriguing nonetheless.
The academic study assessed the literacy level required to follow the lyrics of chart music over time, and found that this has declined so far as to be of primary (junior in US parlance) level, and even kindergarten in some cases.
Can language be safely quantified in this way? That's at least debatable.
The website carrying the report is a left-wing alternative news outlet, and they make a specific link to the monopolization of a handful of huge conglomerates and the homogenisation this produces.
They're referring to the USA, but of course their major media conglomerates dominate media production, distribution and exhibition globally, including the music industry - a process Marxist critics term cultural imperialism, but can more blandly be labeled globalisation.
Even if this is true, does it matter? That's a question for you to decide