In fact I suspect that people are more likely to "do it wrong" in (some?) western populations.

If you grow up in a food culture that is primarily vegetarian/vegan or at least has a subset that is, you immediately have a source of familiar recipes that will likely meet your nutritional needs.

On the other hand, if all you know how to cook and all you've seen being cooked tends to rely on meat proteins for some of nutrient balance, you really need to do some research to know what to add to your diet to replace what you are taking away. This research isn't difficult, really, but it can be hard to know where to start.

I suspect that if you take pretty much any traditional diet and start taking things away from it if you aren't careful you will rapidly run into deficiencies.

I suppose an argument for the recent, significant, western trend to over consumption of macro nutrients has an upside in that even if your diet is fairly (but not seriously) unbalanced, if you eat enough of it you tend to mostly get the nutrients you need....