I’ve eaten high carb / near zero fat years ago for a summer… fruit based and never had issues of insulin resistance. I actually felt the glucose from ripe stone fruits being absorbed by my cells after physical activity. Then ketogenic… high fat / very low carb.
Issues always occured when mixing the two macronutrients beyond a certain threshold.
I also wouldn’t equate fruit with the damaging effects of grains/refined sugar if we’re insulin sensitive… Like after physical activity.