Modern diets are crap, but I couldn't care less, most people who workout or want to eat healthily will do so and people who don't do either won't be using supplements.
The main situation for using supplements, if thats what you want to call them, is losing weight. Because its the one situation where you are eating less food than normal, but want the body to work harder to burn fat, logically the two things simply don't gel together. You can't ask your body to work harder while eating less.
For putting on weight, protein's more than fine, largely because whey is a very very cheap and easy source to get protein from.
But for me, I don't really care what most people want to label these things as. If you want vit e , you can eat it in several foods, or take a pill, its the same damn stuff, and if you need it you need it, its just food packaged differently.
I don't supplement with protein, I need protein, its that simple, I choose for the sake of simplicity and budget, and I actually really like the shakes I make, to have whey protein, rather than burgers, its just food.
EAA's and other things are, for me, a joke, the cost for those substances aren't in the weight, but in the separation. in a 30gram scoop of protein which costs maybe 10-30p, you get more in weight of the EAA's than in a £0.50-1 serving of EAA's from any other source. In other words, throw in an extra 10grams of protein for far cheaper and get the same amount of extra EAA's.
Splitting products up just to get marginally higher percentages of a substance at a higher cost than just having more to start with, makes no sense. Its like chia seed vs Salba a supposedly marginally better "brand" of Chia seed. Its not magically better, if you eat 15grams of Salba, you'd want 16.5grams of generic Chia seed to get the same benefit. yet 15grams of Salba will cost 5 times the amount of 16.5grams of Chia seed anyway, its worthless.
If your diet is poor so called "supplements" will do nothing. If you are trying to get to your peak, certain things to make sure you aren't lacking in can help, but if putting on weight, you're likely eating more food than normal and already a higher intake of nutrients and vitamins anyway. Again I go back to the one real situation to make sure you aren't lacking nutrients, is losing weight when you're taking in less food than normal.