'as fancy as it was' means the stove was not simple or plain. It had a lot of functions that most stoves wouldn't have.
ie. A basic stove has a few functions: turn on/off, timer, basic oven, etc ... perhaps a few other things. A 'fancy' stove can do all this, but a lot more. The term is sometimes mildly negative or derogatory as it implies the object (stove in this instance) does a lot of extra things that are unneeded or unnecessarily complicated.