Nutrition is to me all the nutrients we need to consume. The same rules apply to them all - we need a certain amount of them all, all non-engineered foods only cover some subset of it (hence needing to eat “balanced” to even things out), and we handle abundance of any of them very poorly. “Big food” is not problematic because of what it lacks (getting more of any time of nutrition is easy in modern society), but because of what it has too much of (hard to uneat something). Hence too nutritious. I won’t argue against there being other definitions, but I find this one most appropriate and indicative of the problem. :)
No, your assumption of my definition of “tasty” is not right. Did you like the taste? Then it is tasty. Eating tasty foods is pleasurable, and therefore addictive. And what home cook wouldn’t try to make their food more tasty?
Fats, sugars and salts are shortcuts to maximizing primitive tastiness because “tasty” is meant to drive a search for nutrients and a guidance away from dangerous foods (especially salt giving how rare it can be - ever seen what animals do to get to a salt lick?), but that’s all.
Complexity is itself not tastiness. If a “complex” taste does not make you want to eat more, I’d argue that the food was not at all tasty, but just an interesting experience. Like seeing an art piece that was not beautiful and certainly not something you’d ever consider buying, but still worth having a look at once on a special day.