I have heard that kind of comment about Liverpool before (from people not from the city). I think the main thrust of the idea being that it's seen his best days and there's a certain faded glory/sadness to it.
It really depends on the demographic to a great extent, couple of examples, when I get the train up from Euston on match day it never ceases to amaze me how many young people are travelling up to Liverpool for the weekend, from Euston, Birmingham, Milton Keynes, my London based nieces born in Oxfordshire go up about four times a year, say it’s one of the most vibrant cities they know, not just night life but the whole cultural scene, Tate Modern, Maritime museum, Museum of slavery etc. etc. A few of our friends have children born and bred in London/Home counties who go to/have been to Liverpool University, unanimously positive about their entire experience.
Get to my generation, I don’t have a Scouse accent but whenever I announce that I was born and bred in Liverpool the inevitable old cliche’s come out about unemployment, crime and the odd impression of Harry Enfield's two Scousers eh, eh ! It will die out with my generation though if the City continue I the right direction.