I don't know that it's wrong as much as a bit lame and vague. You need to be rich, an expert cook and have good access to shops to follow that diet.
Going on the "people didn't used to be so fat" theory, a certain amount of natural fat (meat, fish, dairy, oils) and natural wholegrain carbs (rice, oats, brown bread, potatoes) seem unlikely to be the culprit.
What we didn't have before was ultra processed food with artificial sugars, starches, added ingredients, all the fibre pulped out of it and engineered to make you keep eating. Whilst the processed food industry has a massive interest in maintaining profits and lobbies accordingly to keep selling this crap, whilst 80% of supermarket shelves are stuffed with it, whilst takeaways and caterers almost exclusively sell it, most people don't have much of a chance.
If the law was changed so that foods that met the eatwell guide were subsidised and foods in the processed/occasional treat category were taxed, we might get somewhere.