Alternatively (and obviously this is just my opinion) NOT codifying everything opens up more options.
Counterpoints:
1. Most games that "define what you can do" or "codify" things do not have discrete lists of singular actions with no ability to exceed the "codified" list. Instead, at least for well-designed games, they define open-ended
classes of actions, which can theoretically contain an infinite variety of possible use-cases. Thus, it can be a bit misleading to present "non-codified" games as open-ended as opposed to the alleged closed-ended "codified" games.
2. Most "non-codified" or "codify what cannot be done, not what can" games still have a serious limiter on what can be done: what the DM is willing to accept. No game has
absolutely infinite potential for that reason alone. I, personally, have met a lot more people who seem dramatically more keen on placing limits than on embracing possibilities, particularly when it comes to "traditional" or "old-school" play/editions/etc., but I understand that anecdotes are not data.
3. Even when point 2 does not apply, a second limiter exists: the tone of the game and the pitch/premise/principles of the game. PbtA games tend to be hailed as extremely open-ended, frex, but they are only so by leaning
especially hard on these limits. You wouldn't bring murderhobos to a game of Masks, nor plucky manic pixie dream girls to a gritty Fantasy Friggin' Vietnam OD&D game. If the players are already going to be effectively self-limiting to adhere to these things, why not provide rules to make that experience smoother, more natural?
4. Separately from the above: It should not be an axiom that "less is better" any more than it should be an axiom that "more is better." Every choice--including whether to provide many things, few things, or no things--should be evaluated for its
purpose and its
effectiveness. (I.e., it doesn't matter how good the cat food is if you don't own a cat, nor does it matter that a brand of dog food is designed specially for your dog's breed if that food makes her sick.) Chesterton's Fence is in full force here, and it swings both ways.
Note, I do not say this in an attempt to
dissuade you from your chosen game plan (literally a plan about games!) You should play what interests you, and that goes doubly for
running what interests you. I have zero interest in "converting" you to some other position on that front. I am merely responding, rhetorically, to the position(s) declared.