"On the back of" is a phrase I very much intend not to be making use of going forward.
However, on the phrase 'It is what it is', I differ. With slight paraphrasing, I must refer you to the 'iconic' Vietnam War film The Deerhunter and Mike's line "This is this. This isn't anything else".
Whilst not exactly conforming to the wording you offer, it is nonetheless an iconic moment in cinema history and perhaps one of the most unique examples of the skills of Mr de Niro, bettered only perhaps by the Russian roulette scene, where he iconically asks the NVA officer "You lookin' at me? I don't see anybody else here".
So whilst I broadly accept the phrase 'It is what it is', I reserve the right to impose a 'de Niro caveat' if any of the master's immense and truly iconic lines have come close to any which you offer.
Incidentally, I believe John Grisham is working on a novel called The De Niro Caveat. It will revolve around dark intrigue and mysterious happening at the very hub of federal power. John Travolta will play the 35-year-old treasury agent reluctantly teamed up with Navy SEAL Nicolas Cage in a whirlwind ride through a maze of explosions, double cross and betrayal. Robert de Niro will have a cameo role as a retired agent whose highly unique style is to answer all questions by repeating them word for word.
Sorry, I got a little carried away...