Genenerics often have better overheads because the company takes profit on more points of the production and supply chain.

They're also producing products in almost every aisle of the supermarket and gain an economy of scale on things like only needing a single one of eg house style for every product.

It makes sense. When food brands initially took off (1950s?), my impression is that grocery stores were much more regional.

There certainly wasn't anything at the scale of Walmart, Aldi, Kroger, or Publix these days.

Consequently, it was easier for General Mills et al. to use economies of scale to sell quality, profitable products.

Now, it's the grocery stores that can do that.

I think brands just fluctuate in quality as time goes on, they get used to being top dog and coast on brand recognition alone. Mac N Cheese in particular it pays to take the 5 extra minutes to mix your own cheese, but if you don't want to do that Cracker Barrel branded Mac N Cheese (the kind that you finish by toasting in the oven!) is pretty good stuff. And don't forget to add pepper, cayenne, and other spices to store bought stuff, it works wonders!