Most tabletop RPGs don’t bother to have a rule like “characters can’t walk through walls.” It is either implicit or prescribed through having a special ability that specifically allows one to do. Now, an RPG that specifically had a character option that stated “this character cannot walk through walls” would instantly reframe every other character in the game. If only a specific type of character has some limitation that we humans would assume to be self-explanatory, what the hell is the baseline in this game?
Games have implicit or explicit assumptions about their characters. In D&D it is assumed that characters can see, hear, speak, walk unassisted, and so on. These capabilities can be taken away but only through very specific rules interactions. A character’s ability to see isn’t marked until a player says that they would like to play a blind character.
I don’t even know where I was going with this. This started out with me thinking about how funny it would be to make like a supplement for a game that features these really strange and specific abilities that suddenly change the assumptions of the game. Like, a supplement that has a creature with an ability like “Floorwalker: this creature can walk on floors.” Because none of the other creatures in the game have that ability, it’s now implicit that they can’t walk on floors.
Anyway if anyone would like to help me salvage this post by saying something insightful go right ahead, I’m gonna go make some pasta.
Sure, I’ll take a crack at something insightful: this truth was part of the reason that D&D 3.X ultimately failed at what it was trying to do.
The thing about 3.X was, every couple of months a new book would come out with a bunch of cool new mechanics for things. But the problem was exactly as described in the post: every time they came out with a cool new mechanic for Doing The Thing, it meant that you couldn’t Do The Thing without that mechanic any more.
A perfect example of this is the Fling Ally feat from Races of Stone. Suddenly, hooray, there’s this cool new feat that lets us do the cool Fastball Special thing! Except… now you couldn’t do it if you didn’t have the feat. And before that, throwing an ally wasn’t something that necessarily required a particular feat. So now, because this new character option came out, you couldn’t do the thing any more.
This also led to a situation where, because a character only gets so many feats/class abilities/spell slots/etc., they couldn’t do all of the things they wanted to because they didn’t have enough of that character building resource to get all the ones they wanted. (Or, more commonly, to both get the ones they wanted and to keep up with the freaking nuclear arms race that was character power scaling in 3.X.) So the new character options wind up making characters less cool by taking away options from the players, even though in theory these new options increased player choice.
4E got away from this by simply not caring enough to simulate large parts of the game world, which is fine, 4E is a very specific game designed to create a very specific experience and it does so really well.
5E has dealt with this, basically, by creating as few character options as it possibly can and then telling the DM, “Make it up!” This does fix the problem, but introduces two new ones: 1) this is a ton of work to put on a D&D DM’s already overloaded shoulders and 2) there’s practically no way to ensure the solution carries from group to group, so that work has to be redone constantly and likely in ways counter to existing expectation. Which… doesn’t seem a lot better, when you think of it like that.
There’s a lot more to say about this topic, mechanically speaking. (For example: the matter of making up a mechanic so effective that the party insists on using just it over and over.) But hopefully that provides some insight into the tension around floorwalking and player options.