Unrefined carbs like in potatoes and (whole)wheat and oatmeal etc. are not bad; those foods provide many good nutrients and do not cause the negative carb effects you mentioned.
It's the same as fruits containing sugar (which is a carbohydrate actually I think) but not causing the same ill effects as eating the same amount of sugar from Sour Patch Kids (candy which is ~80% sugar by weight).
That's the thing that everyone in this discussion seems to be missing: taste. There are good reasons to believe that better-tasting food may have physiological effects beyond just being pleasurable to eat [1]. This is not controversial when it comes to other substances but with food it's a much tougher battle.
[1] https://slatestarcodex.com/2017/04/25/book-review-the-hungry...
The problems start when you refine all the fiber away and load them up with oil.
Fasting is a powerful thing! So is refined sugar.
It is also very easy to eat a large number of calories via carbohydrate. Essentially, carbs make you fat.
I can personally observe in myself that if I eat a chocolate bar in the morning, I will be more hungry in an hour or two than if I had eaten nothing at all.