I dredged up some information on how Mutt Lange writes. Or at least how he did with Bryan Adams (who by the way sounds a little like Joe Elliot).
Bryan Adams Interview | Bryan Adams Anthology | Bryan Adams Songs
Based on Mutt's work with Adams and Shania Twain, I'd say he maxes out at generic love songs and never makes lyrics great.
Anyway, back to Def Leppard specifically, I'd heard of the remakes before, but had not listened to them, because I'm against all that. Joe Elliot's voice has deteriorated, and it's erratic. The "Rock of Ages" remake makes that too clear. The remake also lacks the musical layering that helped make old Def Leppard songs great.