“Then the Lord rained on Sodom and Gomorrah sulfur and fire from the Lord out of heaven; and he overthrew those cities, and all the Plain, and all the inhabitants of the cities, and what grew on the ground. But Lot's wife, behind him, looked back, and she became a pillar of salt” (Genesis 19:24-26 NRSV).
I think your interpretation of this familiar story is quite valid, and the point is uncomfortable but important. Scholars believe the entire Sodom and Gomorrah story is a religious interpretation of an historical event – a natural upheaval of some kind that destroyed those two cities but left others – like Zoar (Genesis 19:21-23) – untouched. Interesting, but whatever the history, the meaning is powerful at a metaphysical level.
Divine directives must be obeyed without question. The directive in this case was to move forward and not to look back. How often do we get that directive, in one instance or another! Our mortal minds are attached to the comforts and pleasures of the present, but our spiritual guidance is guiding us forward. By looking back, Lot's wife allowed mortal attachments to become more important than her guidance. The same thing would happen much later, I think, to the Hebrews wandering in the wilderness. So long as they kept looking back at Egypt, grieving over the foods and other pleasures they'd left behind, they were lost in the wilderness. It's only when the generation that remembered Egypt died out – except for Joshua and Caleb, who consistently believed and looked to the future – that a new generation of what Charles Fillmore described metaphysically as “thought people” were willing to turn their faces forward and leave the wilderness behind.