Regardless of this new evidence people have been eating carbs for at least 10000+ years. The obesity epidemic has only really started the past 30-50 years. Whatever has caused people to get super-fat, it wasn't carbs.
The resulting insulin production inhibits fat oxidation and increases fat storage.
https://www.youtube.com/results?search_query=fung+obesity+ep...
https://www.biolayne.com/articles/research/its-not-calories-...
Whatever is available in the stores is not the same thing we ate 100 (random number) years ago.
And that's not limited to wheat, but I reckon most commercially available fruits and vegetables are much worse than their counterparts grown organically in one's own garden. They certainly taste much worse.
Carnivore is much maligned still, but I bet the reason it works so well is that you avoid eating an unknown amount of chemicals that are routinely sprayed on unripe plant matter, which has to count for something.
A slice of cake is, in fact, an "excessive amount" - it's more food than a pound of cheese.
Eating a pound of cheese does, indeed, feel "excessive", while a slice of cake (or two) is just a chaser after a full meal for most people.
Diesel fuel has a huge amount of calories, but your body obviously can't process it properly.
What processed food brought is very unnatural combination of a lot of refined carbohydrates and a lot of fat especially in the form of polyunsaturated seed oils. Seed oil consumption in substantial quantities is relatively new thing (like 100 years). And even olive oil (with its rather low polyunsaturated fat content) was never staple food. In Ancient Greek literature, for example, there are more references to its usage as cosmetic or for lighting than for eating.
But it's a significantly bigger problem today, so people are trying to point out things that have changed after the invention of writing.