(I had planned on writing another post for part two, but this is an interlude triggered by another Discord discussion, so here we are. You may or may not find part one useful).
It is always useful to tease out the assumptions of a thing you're designing -- as an exercise if nothing else. Michael Brough for a while made an art of taking an assumption about roguelikes and turning that assumption into a whole game, whether it is character progression or inventory systems.
As I'm making a TTRPG, I've been slowly working through this myself - specifically "why am I making a TTRPG?". There's one straightforward answer: creating a tabletop role-playing game is extremely easy. Far easier than making a video game or board game. All you need is some kind of desktop publishing software, and a page on itch.io. And not only that, but you can be deliberately as expressive (glass of water as a hit point mechanic) and ambiguous as you want to be. I've spotted rule omissions in other pre-release TTRPGs, only to be told by the designer "Your play group can figure it out" and the beauty of the genre is entirely that you can. I've made a complete TTRPG from scratch and published it in under 2 hours.
"But how did you play test it?"
And that's the problem. Because the document as written isn't a tabletop role-playing game. None of them are.
Table top role-playing games exist in a space somewhere between board games, LARPs and their own unique thing - and they are hugely influenced and indebted to both. Inevitably I have ended up asking myself repeatedly "Would this be better as a board game?" or better as a LARP, and while I can try to answer those questions myself, I would expect other people to be asking those same questions and coming up with much more coherent answers than I could.
Let's start with the rules. Board games generally don't work if the players don't know the rules. But knowing the rules is the exception rather than the rule in the (traditional) TTRPG space. And while you could argue that more modern TTRPGs have tried to address this by simplifying the rules - these games can still work if you are entirely ignorant of them.
Well, if we're able to ignore the rules, there must surely be solid documentation about the practical process of playing the game. But it appears that LARPs do a much better job talking about this practice of play than TTRPGs do. The recent series on Dice Exploder about LARPs highlighted to me how sophisticated the thinking is in that space, whereas I can't see comparable writing about tabletop games (either board or role).
I think this is as a product of (paradoxically) how hard it is to get into the practice of tabletop roleplaying design. There is "no one place to go" because of the small size of the industry, and the way it keeps being shaken up by technology transformations out of its control. You used to be able to go to the Forge, then it was Google Plus for a while and now the majority of people have retreated to Discord, which has its own challenges for new entrants (being private by default, transient and moated to protect its communities -- attributes that are important to preserve those communities). Sure there is RPG.net, but it's much much clearer to me where to go for roguelikes (which are smaller again) or boardgames (which are bigger).
My recommendation as to where to start, after having spent a while looking, is podcasts: specifically starting with the Design Games podcast which does a great job going top to bottom on a specific design practice, then Dice Exploder which provides a zoomed in view of the history and practice of a single mechanic, then Read the Fucking Manual if you want to hear smart and thoughtful people with strong opinions talk about whatever they want to in the role-playing space, and around it.
So let's go back to my earlier bold claim that no tabletop game has ever successfully been written down. It's entirely impossible to enumerate all the circumstances a game can be played under, but in a board game, we can usually notice when the game breaks down because the rules don't work as written ("hey, you took my cards when I went to the kitchen for more snacks"), and in a LARP, a lot of work has been done to make sure that the game runs as intended ("the rules have been written in tears"). Tabletop games kind of fall in this weird middle between these two extremes, carried on the momentum of 50 years of playing D&D such that every other TTRPG is pulled along on its coat tails. But I think that's their strength.
You don't learn a TTRPG in isolation. You learn at the table. You watch actual plays. You learn go on to unlearn a whole lot of stuff that you learned when you change from one system to another. TTRPGs are accessible in a way that LARPs, and even board games aren't. Sure, there might be a need for a session zero, but there's no concept of teach the game the way that board games sometimes require. TTRPGs thrive on vibes.