Games come alive in play. Designers can write anything they like in rulebooks, but it’s GM’s and players who actually implement it, who actually play the game, and who actually decide what the game is.
Designers have little control over how the game is actually played.
There’s the example of Gary Gygax, designer of Advanced Dungeons & Dragons. He made a lot of rules, rules he pretty much followed, but many of which were ignored by the player base. The real game, as it existed “in the wild” differed from the Platonic ideal (as it existed in Gygax’s gaming sessions and Gygax’s mind as the designer).
Use evinces utility. If people use a rule, it’s because it’s useful. (Or how they implement it is useful.) If they don’t use a rule, the rule isn’t useful. (Or they don’t understand the rule, because the designer didn’t describe it clearly.) Players and GM’s determine whether a rule is used, and hence what the game is actually like in play.
This means game designers cannot predict or dictate the game’s gestalt. The gestalt of the game is how it operates as a whole. The feel, or the mood and experience of playing the game emerges from its gestalt. The gestalt of Call of Cthulhu is different than Savage Worlds, which is different than Shadowrun or AD&D. More, the gestalt of any given game varies from group to group.
The label “Old School Renaissance” is all about the gestalt of the game. “Yes, playing Adventurer, Conqueror, King is strongly reminiscent of how we played OD&D/AD&D/RC back in the day.”
OSR games are knowingly designed to produce a gestalt which resembles that of vintage editions of D&D. The designers have some influence, but cannot absolutely dictate, what their game’s gestalt is.
Here’s the upshot: Game designers are at the mercy of GM’s and players. They determine how your game is going to be played.
This is a good thing. You shouldn’t try to dictate to players and GM’s. To the contrary, you should try to understand what people find valuable and fun about your game (or RPG’s as a whole), and enhance those aspects.
Rules falls by the wayside. This is inevitable. Rather than raging against it, accept it and use it. Find out which rules are disused, determine why, and either get rid of the rule (streamlining your game) or alter it so it’s useful.
As a game designer, you are not the master. You are the servant. Suck it up, accept your role in the universe, and help your players and GM’s. Do it well enough, and you might actually be able to make a living at this.