That's it! The desert stands for what is opposite to the world,
the lust of the flesh, and the lust of the eyes, and the pride of life (1 John 2:16). It is the condition devoid of (tasting) the water of conceit, the provoking of our neighboor to anger like wild animals or backbiting them with the poison of envy like snakes (Gal. 5:26)... and yes, not making the belly our God (Phil. 3:19).
As to the original question, this may come as a surprise, but the Septuagint version of the passage in question doesn't say that God will destroy the righteous along with the wicked, but rather the transgressor and the unrighteous.
Ezekiel 21:
2 Therefore prophesy, son of man, set thy face steadfastly toward Jerusalem, and look toward their holy places, and thou shalt prophesy against the land of Israel, 3 and thou shalt say to the land of Israel, Thus saith the Lord; Behold, I am against thee, and I will draw forth my sword out of its sheath, and I will destroy out of thee the transgressor and unrighteous. 4 Because I will destroy out of thee the unrighteous and the transgressor, therefore so shall my sword come forth out of its sheath against all flesh from the south to the north: 5 and all flesh shall know that I the Lord have drawn forth my sword out of its sheath: it shall not return any more.