Reality is anything but boring.
It encompasses everything in nature, after all.
Blake, were he given the opportunity, would likely qualify his statement to say that he meant quotidian reality only was ‘vegetable.’
The imagination is important because of the tedium of the ordinary. This is why the arts are necessary. They perform a vital function: the preservation of our collective mental health.. ‘Purposeless’ daydreaming provides a vacation from the everyday, the stressful, and the horrifying.
The image making faculty of the mind is also how he reshape our reality to better suit our natures. Science and engineering follow the fantastic promptings of the unconscious.
Our daily reality is constantly being shaped by the whimsies of creative minds, ironically becoming increasing less ‘vegetable.’