Who wanted instruments to get in the way of a voice like hers?
The song is considered a rejection or critique of consumerism, which was in part the credo of 1960s hippies. Consumerism can mean being aware of and getting informed to make good decisions when spending money. But the definition here is about mindlessly buying more and more stuff, that isn’t really necessary to live a fulfilled life.
This is for debate, but in this song, Janis may have been feeling unable to keep up with the Joneses, who all had better things than her. And so she asks God to provide shiny, expensive luxuries. Of course, God doesn’t do that; God wants you to give it all away! And thus is Janis dismissing the vain accumulation of those around her in an ultimate manner?