I saw that when it was shown - basically, it said that music and lyrics were both becoming less complex. Because, after all, nothing Adele's written can touch the lyrical and musical complexity of James Brown's "Sex machine". Oh sorry, that's wrong, the examples given were equally facile in the opposite direction, which was a shame, because cherry-picking examples slightly undermined the premise. I don't disagree with that premise though.
Rock wasn't in an unhealthy state before punk, but it did provide new musical DNA which was incorporated into the mainstream.