Appropriate Total Calories is STILL the most important thing.

Nothing is more important than "Appropriate Total Calories".

Or more accurately, "Appropriate Total Calories With Adequate Protein".

Often and to this day you'll still see people suggesting or even insisting otherwise. It's not calories, it's food quality. It's paleo vs processed. It's inflammation, alkaline pH, whatever else.

Nonsense.

It is Appropriate Total Calories first and foremost.

Very simple logic:

• The appropriate & required amount of energy intake from whatever choices of foods is going to facilitate better performance and produce better condition than one quarter of that amount.
  That's obvious, surely?
• The appropriate & required amount of energy intake from whatever choices of foods is going to facilitate better improvements in condition than twice that amount, if you're NOT deliberately "bulking" and deluding yourself that that's an improvement in condition.
  Again that's obvious, surely?

So you could argue that "2000 calories of these foods will not produce the same result as 2000 calories of those foods", but it'd be a hell of a lot more similar than 2000 calories of anything vs 1000 or 3000 calories of anything else. Right?

Now though.

WITHIN that total energy intake, you can make wise strategic choices in the interests of not being deficient in required nutrients, and perhaps also increased Thermal Effect Of Food via higher protein and fibre.

You should also consider any choice that facilitates good & enjoyable, prolonged adherence to the program a wise strategic choice. If that's a chocolate biscuit at supper time so be it.

If total calories are optimal relevant to requirements (or at least, somewhere within an "adequate but not excessive" range), protein is adequate to optimal, fiber is sufficient... if you're including cereal grains, vegetables, fruits, nuts &/or legumes you're likely not deficient in any micronutrients and you therefore have a healthful diet that will facilitate good performance and condition as an adaptation to a good training program.

Of what else there is that people talk about as being "as or more important"... it varies from complete nonsense (paleo, alkalinity, and so on) to stuff that may matter but is impractical to attempt to micromanage, and is likely an unproductive distraction from what is more practical and more productive to focus upon, as described above.