> Good taste is an incentive to satisfy something more primary,

Covered in my comment above: The more primary drive is that those are high calorie foods. A drive to consume more high calorie foods is beneficial in times of food scarcity, like the past.

Cutting sugar doesn’t kill 100% of the gut biome either. It doesn’t kill gut biome at all, actually, it just changes some of the proportions. Those parts of the microbiome are most likely still there, just in different ratios.

Antibiotics are a far more powerful and faster modulator of gut biome, therefore if the above was true we’d see similar effects occurring more rapidly with antibiotics than diet.