The solution might be a Myers-Briggs-style assignment for a game. To my mind, the advantage of such a system is that every IF/game has the same number of digits in its signifier. Let me fling out some ideas:
Is there a Map the player can wander on, or are we moving between story Junctions instead?
Are individual outcomes guided by principles of Character stats or of a Narrative reality?
Are the moves made on a Freeform command line, or is it a list of Options?
Is the action built like a repeating Game cycle, or Unbounded turns? Is there a central loop that keeps repeating, or is the player able to move around at will?
Are the obstacles based on Puzzles, Story, Tactical choices, or Resource management? What is the player up against?
Is the game Linear or Branching? Is there only one good ending (with varying degrees of success), or are there multiple good endings?
A game like Zork is therefore MNFUPL. Map-based narrative action (not stat-based), free-form command line, unbounded turns (no game cycle), puzzles, and largely non-branching (there is only one good ending).
Yes, you could get into some unholy squabbles about how a game is rated on the particulars. Peoples’ opinions will differ. You could always use lower-case letters to indicate the distinction isn’t particularly strong in favor of one or the other choice; or use X when there is a complete balance between them.
The point being, a system like that leaves room for many varieties of IF games to be assigned an indicator that better describes its working mechanisms.