I'm certainly not genetically gifted for bodybuilding, but insulin along with my highest-ever daily carb intake got me to my biggest and leanest offseason, peaking at 259lbs., and it helped me put on 18lbs. LBM, Dexa-verified, over the last 12 months. I actually didn't tolerate carbs well early on, but as I've continued to improve my body composition through the years, added more muscle and stayed leaner all year, I've handled them better and better.
I did a lot of reading on insulin use here and other places before starting, and you read many accounts of getting fat, bloated, holding water subcutaneous water, etc. But I question how many of these people put themselves in the right position to get the most out of it.
If you're not single digit body fat and coming off a period of lower calories, particularly lower carbohydrates, you're not putting yourself in the best position to benefit from insulin. Nobody should be surprised that insulin made them fat if they start it 2/3 the way through their offseason when they're already over 10% body fat.