I prefer discussing "crunch heaviness" more in terms of a Likert scale gradient: i.e., light, light-medium, medium, medium-heavy, and heavy. There is a lot of gradient between those sub-categories as well. We may even want to add the categories "Ultra-Light" and "Ultra-Heavy" to describe some.But that's the correct answer - it's the very definition of mid-crunch! If Fate or Cypher System are rules-light, and Pathfinder or HERO is rules-heavy, D&D 5E is squarely in the middle.
I prefer discussing "crunch heaviness" more in terms of a Likert scale gradient: i.e., light, light-medium, medium, medium-heavy, and heavy. There is a lot of gradient between those sub-categories as well. We may even want to add the categories "Ultra-Light" and "Ultra-Heavy" to describe some.
I personally prefer a 44-point scale. Some divisions include light-light-light-medium-medium, light-light-light-medium-medium-medium, medium-medium-heavy-heavy-heavy, and so on.
But what's the mechanic for differentiating between a 27 and a 23? What if the rules are published in 3 small books vs one large book? Is there a bonus for a searchable PDF with a table of contents? I'd hope that the system models using common language names and pictures for game concepts as opposed to using legal game terms. Do bonuses for table of contents and searchable PDF stack?
Or do you just assign the number by GM fiat?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.