Here's why:
* Hyperbole: Exaggeration used for emphasis or effect. The sentence uses hyperbole by describing the land as "the flattest, driest, most barren, depressing, arid wasteland". While it's possible the land is very dry and flat, the use of multiple intensifiers ("flattest," "driest," "most barren," etc.) greatly exaggerates its negative qualities.
The sentence emphasizes the bleakness and desolation of the land, making it clear that it's an unappealing place.