It roughly translated into ‘the sound of the guitar mixed with the tree imagery is too nostalgic-sounding’. I’m still scratching my head on that one.
A really good translator might have written that as "Your artistic choices are dated", which is probably what the original author meant to convey. The word invariably translated as "nostalgic" is natuskashii (懐かしい) and it conveys an impression of times-gone-by, which is sometimes not a good thing.
(I once read a delightfully poisonous review of UI decisions by our senior engineer, beginning with "The new interface to the web app reminds me of my childhood experience working with mainframe terminals, except without the complex functionality.")