That is an altogether different thing than saying all roleplaying games are based on "Improv Principles"
If a given game presents people the open ended question of "what do you do", its fundamentally integrated an improv game. There isn't a single game in the RPG space that doesn't do this.
I would argue that blocking is fundamental to the play experience of the vast majority of roleplaying games (traditional, OSR and indie).
Which is what I'm talking about when I say there's a problem with the space not recognizing that RPGs are fundamentally improv games. Blocking isn't a good thing, and its the root cause of every single issue in the hobby that people keep inventing new jargon for.
The basic purpose of most mechanics is to resolve what happens when one participant tries to block an action of another in a way that does not rely on consensus. I try to do X, but it might not succeed and instead something else that I might not want to have happen might happen. That's what makes these games so exciting - the prospect that things might not go our way.
Blocking isn't the same thing as failing at something you wanted to do.
The big thing about why blocking is such a perverse problem is that RPGs are three way improv experience. The GM, the Players,
and the Rules are participants in it. You have to Yes,and the Rules and they, in turn, have to Yes,And you.
The possibility of failure is a part of that. Where it goes wrong is when the Rules completely prevent you from taking a reasonable action to begin with because they don't integrate the abilty to improvise properly, and if/when you end up with no organic way to move forward when that occurs. And most often, its usually the GM that begets failure as blocking, because they set an unreasonable requirement to force a specific outcome. (Eg, its all Railroading all the way down)
Failing forward is a generally good idea that goes towards addressing that, to be clear, but it goes wrong in what its called and how its implemented. The thematic railroad of indie games isn't any better, and the notion that its "failing" often is counterproductive in that it produces a really questionable gamefeel when people internalize that that occurence is them failing. Its not that fundamentally different, in effect, from people in traditional games who end up feeling like a moron because of what the dice say, and this is yet another example of why the failure to recognize is so perverse.
Blocking is at the heart of every common issue with these games.
It seems to me that blocking is necessary to create gameplay.
Not at all. Blocking is easily understood from the perspective of disruption. In a traditional improv game, we can observe how awkward a scene gets when a player inadvertently (or purposefully, as it were) blocks their fellow participants, and especially so if none of them have the skill to smooth over it as it happens and recover the momentum of the scene.
This manifests in RPGs as all those things I've pointed to before. Railroading, plot or thematic, the Failure/Moron effect, the "Writer's Room" of indie games, and so on. And indeed, from a game's perspective, Rule Zero is blocking, and one only needs to look at DND5E for an example of what happens when a game actually manages to block itself by being poorly designed. The Martial/Caster disparity and the Adventuring Day are such examples.
These all disrupt the gameplay and kill the momentum of the experience. Sometimes participants may just suffer these ill effects in silence, and naturally the game has no way to speak for itself unless the blocking was so egregious it just straight up breaks (ala 5e), but that doesn't mean blocking isn't bad or just part of the game.
For example, consider the following situation.
It's not clicking for you because the example is bad and isn't what blocking is. Person 2's response could be interpreted as a prompt for the speaker to explain more about themselves, establish rapport, or give a reason for why they should be listened to. It’s more of a conversational obstacle rather than an outright block, leaving room for further negotiation or engagement in the conversation.
The key distinction is that blocking implies an intentional barrier to interaction, whereas this situation is more about setting a condition or acknowledging a lack of familiarity that could lead to further conversation if addressed.
What would actually be blocking in this case is if the GM, at every attempt to interact with somebody, contrived a reason to deny it outright no matter how you approached it.
I'm inclined to point towards this particular amusing little video:
The DM's meltdown at the end was a great example of what blocking actually is, but given the intended nature of most DND Campaigns (ie, the expectation that there is a specific if open-ended plot to be pursued), the Players were actually blocking the DM in turn by never engaging the obvious plot hook (nevermind the things they did that isn't in the purview of their role as Players to begin with) and by not allowing to him to participate, and the game being what it is, doesn't give the DM any substantial means to account for all their improvised nonsense anyway, which inevitably leads to the meltdown.
People often watch that and see it as an indictment of huge tables, but really that wasn't the issue. It was a failure to respect the input of the three Participants in the improv game, and it doesn't really matter how many actual people occupy to the two human roles.
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Another thing that should be pointed out here, about the fact that RPGs are fundamentally improv games, is that they are not
only improv games. Bespoke mechanical systems have been endemic to these games since the beginning, and this is
why the Rules are a participant, and what I'm ultimately talking about when I refer to games not integrating improv and systems together properly.
If a game isn't designed with this integration in mind, it puts an undue burden on GMs and/or Players to have the improvisational skill to smooth over and work past blocking.
A better way forward, as I've argued, is just not doing this. Integrate the two properly, and prevent blocking from manifesting at all, at least on part of the Rules. Even in my game, a GM or a Player could still do it, but I make it a point that playgroups need to establish a specific Game Tone for themselves, so that there's an established boundary to where they can take the game through improv, and the game itself is designed to yes,and that choice whatever it may be.
Whether you go looney tunes wacky or game of thrones gritty grimdark or anything inbetween, the game isn't going to block you. Course, the caveat is that if you block the game, the game will break. No silently suffering game here, as its been designed with heavy integration between all of its elements.
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That all said, it does prove prudent to point out that at this point I don't actually call my games RPGs anymore anyway, given just how deeply entrenched all this baggage is (can't count how many times I've had people elsewhere straight up tell me I'm not making an RPG, so I just embraced it).
I call them Immersive Improv, which better describes what my games do and has been designed to provide for, which has been nice if only because I no longer have to concern myself with saddling the game with said baggage, but also because I've observed that change actually making the game click better for people coming from RPGs.
(Which all then just begets people who question why I bother coming into RPG spaces, which is just sad, rude, and incredibly gatekeepy. Yet more reason I generally consider these spaces worthless unless I just feel like getting into it or want eyes on the things Im doing)