You can actually dramatically increase how you perform on a 5-hour OGTT by reducing fat intake and eating extra carbs, which speaks volumes about blood sugar regulation and diet. Having said that, your body is your experiment, and requires an open mind, minimally-polluted by scientific ideas.
How have you been eating? Have you been exercising? How have you been sleeping? I would be interested in hearing these things before “blaming it all on carbs.” I suspect you’ve been eating a high fat diet, not sleeping well, and not doing much physically.