What I meant when I raised the specter that D&D might be too self-referential is this very concept of the game becoming its own inspiration, developing too much of a "canon" that players must invest in and learn before they can understand and enjoy D&D. There are a number of ways this occurs in post-original D&D.
- Speciation (turning unique individual monsters first into a type, then into a common species, possibly with an entire economic system based around them.
- The equivalent Genericization of other items (stores that specialize in spellbooks, mass-market potions and swords +1, etc.)
- Industrialization of magic (lighting cities with thousands of Continual Light lamposts, for example.)
- Over-Systemization (creating equivalents of every class, monster, spell, etc., for each alignment, terrain, element, ability score...)
- Jargonization (turning system-level terms into "creative" elements and elaborating them into new classes, monsters, spells or other fictional elements.)
And so on. To a certain extent, combining or inverting ideas that already exist to come up with new ideas is a fine idea, but to then canonize these inventions, and their derivatives, and let them take over as the primary creative engine leads to overly-elaborate and rather bland game supplements. The article on familiars that James cites is a good example: the author looked at the list of special familiars in the Find Familiar spell, decided that there weren't enough familiars for every alignment (over-systemization,) and created very artificial stand-ins for the "missing" familiar types. Another example is the plethora of "buff spells". Once the general concept of adding a bonus to an ability was created, "designers" came up with equivalent "buffs" for everything in the game that could be expressed as numbers. The decision was made to "fill the void" left by stats that didn't have buff spells yet, instead of thinking about magical transformations that could indirectly improve various stats.
It's my feeling that players should be looking for ways to make their characters stronger, not looking for things that add a bonus to Strength.