Maxperson
Morkus from Orkus
They weren't designing the game in place of something incomplete by creating those random tables for two reasons. One, tables are not required for complete rules. I can't remember the last time I used a random table for an encounter and didn't just pick the monster. Two, since it's a preference and not a lack in the rules, creating a random encounter table is done to make the game the DM's own. It's an improvement to him.Since I'm positive that you've played with DMs who make up random encounter tables when they're not built into the modules already, and who fill in rules for jumping when the distance you can jump is unclear (see above), I'm certain that you must simply be in a semantic argument with someone over whether that counts as rule 0 or someone else.
The rules for NFL football are also complete, yet you still need several refs. Referees are not a sign of completeness or incompleteness of the rules.I don't have a horse in that race, but wish to state: you can play chess (for example) without a referee because chess is "complete" in that from a legal game state, the rules will never fail to tell you what the game state is after a legal move. Chess is closed in a way that cops and robbers is not, and which D&D would not be if DMs were not authorized to spontaneously improvise. When someone says Rule 0 is necessary to complete the game ruleset, this is what they mean.
The game provided rules for that, though. There are rules(guidelines) in the DMG for creating new races, classes, etc. for play. That hobgoblins weren't a PC race at the time that happened(presumably) doesn't mean that the rules were incomplete. Further, there were rules for persuasion of NPCs, taking attitudes into account, alignment to help you with the decision, and so on. The lack of a rule stating specifically that if a hobgoblin is asked to become a Sith apprentice there is a 22.6% chance of success isn't a hole in the rules.When the players capture some hobgoblins instead of killing them, and a player says he wants to sit down and talk one of hobgoblins about how cool magic is in hopes of making the hobgoblin want to become essentially his Sith apprentice and learn magic... No 5E rule will tell you the probability of that Hobgoblin eventually becoming a 1st level Sorcerer. And yet it happened! I had to improvise rules for it, and some people will say I did so under Rule 0. Others may call it something else, but whatever you call it, it was necessary because the game was incomplete w/rt the probability and methods of hobgoblins becoming magic-users.
As the DM once you used the rules to determine if the hobgoblin was interested, all you had to do was pick the sorcerer class just the same as any other PC. Or go with an NPC sorcerer stat block. In the MM all of the spellcasting NPC statblocks state (any race) which includes hobgoblins.
Rule 0 wasn't necessary to figure that out. Now you may not have been satisfied with the rules provided and wanted better rules, but that's not a sign of incompleteness, but rather of you wanting to make the game your own and improve upon how such a hobgoblin would become a sorcerer.