Lyric discussion by Human-beef 

Cover art for London lyrics by Alanis Morissette

It's sarcasm. The lyrics are not logical, but the song describes a particular state of mind. Perhaps she just experienced this state of mind in it London.

You know, that feeling where you are so tired and drained that you don't have the energy to do anything, and you begin to notice little, insignificant things? It's like nothing matters and everything feels grey and pointless.