He's not. He's 37. His keeping has never been outstanding and it's declining. His batting likewise has been dreadful. He had a magic summer last year but he has scored 71 runs in 6 test matches since then. even since he came back in the side last year he is averaging sub 30 in test cricket, despite that home series last year.Haddin always struggles in situations like this because he always looks to play very straight. The second new ball was nibbling around a bit and light was fading.
Still our best by a light year.
Nevill scores runs and keeps well in f/c cricket, as does Whiteman, Hartley and others. There are numerous options to replace him. The only thing keeping him in the side at present is Clarkes dodgy hamstring and the lack of other captaincy options, given Smith is still establishing himself and no one else is an option.
If you think Haddin is light years ahead you are deluded.