Not a good comparison, in my opinion.

KTF came out in 1992, the same year Def Leppard released Andrenalize, which was also very successful, but very much in line with Lange-era Leppard sound-wise.

Slang came out in 1996 and had a lot more grunge influences, while the genre was already on its last legs. If anything, it was already outdated, as Cobain was obviously already dead and Pearl Jam was moving away from classic grunge sound with No Code album, which sounded more like garage rock. Slang is darker than Leppard's other stuff and has some diehard fanbase appreciation, so on that regard, it's closer to being a Leppard's These Days-equivalent, rather than KTF.