Glycemic Index Question

I’ve heard various conflicting things about the GI

some people say that a diet should be made of mainly Low GI carbs (excl post workout drink of course)

others say it it’s not such a good measure cos eating combinations of foods have different effects and it’s eating whole, unprocessed foods that are important.

So how seriously should one take the glycemic index? I mean oatmeal isn’t that low but it’s a staple of any athlete or bodybuilder’s deits as carbs go right?

Sure don’t eat cakes or refined bread or flour or white rice but what about natural foods like potatoes or stuff like brown rice?

Anyway hopefully someone can give some decent insight into this.

Thanks