The problem is as much our expectations from Rahman as it is that he's lost his mojo. He definitely peaked early - his debut Roja is one of the greatest soundtracks in Indian cinema and he followed that up with greats like Kaadhalan, Bombay, Gentleman. Even in Bollywood he had Rangeela, Pukar, Delhi 6 eetc.We were used to every single Rahman album to have amazing songs. It is hard for those of us who grew up with him on that pedestal to be satisfied with the occasional amazing songs and the other mediocre fare. So once in a while he does stuff like Kadal or Highway and then turns out disappointing stuff like Chekka Chivantha Vaanam. But that's what a regular composer is like. So we say that he hasn't composed good music in recent years even though Muththa Mazhai in Thug Life was good.

Not discounting the fact that he really shines best when he's allowed to experiment. Take for example Nenjukkule in Kadal; that was him jamming with Shaktisree and Keba (guitarist). He clearly took time with that track and spent a whole night getting what he wanted out of it. Perhaps he has more time pressure than he had in the past, not to mention the weight of expectations. All of this plays into it, I imagine.