Is there a meaningful distinction to be made between the system and the content?

[PhoenixPhyre]

This seems about right, although I think I’d put D&D higher up, at least 5E in particular. To me the character classes - the presence of warlocks, paladins, druids etc - really strongly implies setting. And the differences between the classes and the experience of playing them is pretty close to the mechanical core of the game imo. They are mechanical objects but they are very much content at the same time.

Also, your mention of “conforming settings” is interesting. If I understand what you mean by that then I think it would probably be impossible to design a game at level 0 on your scale, as you described it. I suspect that if you set out to design a *completely* generic RPG, it will still lean towards certain genres, or not even genres but game feels, depending on your design choices. I might be wrong about this but my intuition is that even “roll a d20 and add a modifier” vs “roll a pool of d6 and add them up” is going to affect whether most groups want to use it for, say, light hearted anarchic games or more serious fare. I’m kind of out on a limb here, but I think Risus is a good example of game that aspires to level 0 and actually reaches level 4 or 5 on your scale.

Yeah, I'd separate genre from feel. The endpoints (0 and 110, the latter chosen as "this one goes to 11") are intentionally "off the scale"--you really can't get there and still have a functional system[1]. I'd put "doesn't tell you a genre, but does tell you a feel" at roughly 10. Feel is a weaker constraint than genre, but it's still a constraint (so not a 0).

I think so…? Or I think the level of concreteness with which setting, scenario and characters are defined will usually match. Like, most PbtA games tell you enough about their setting that your take on it is going to fall within pretty clear limits, but it’s still a setting that you make. And then the playbooks don’t amount to full-on pregenerated characters, but they do have a lot to say about what kind of person the character is and their role in the narrative, not just their abilities. I actually think I’d put most PbtA games pretty straightforwardly in about the 70s on your scale. Blades is the 80s, Lady Blackbird getting close to 100 (and I’d cap it there).

EDIT: But a few seconds after posting that I’m already doubting most of what I said, lol. It’s an interesting way of thinking about games in any case.

EDIT 2 and then I promise I’ll stop: I would add two more terms into your flow so it goes:
System -> feel -> genre -> setting -> scenario -> characters.

Feel is sort of tone, atmosphere, vibes. Genre is genre of stories the game tells, defined fairly broadly.

I agree with this, mostly. Feel is definitely weaker than genre, but I think that feel and genre aren't necessarily weaker than setting. Because you can have the same setting where some stories/scenarios in it have very different feels/genres than others. I think they're parallel tracks, both feeding into scenarios. At least when you take the large-scale view of a setting (ie an entire world that could be real, even if you only use a piece of it for any given story/campaign/etc). They're not entirely independent--you can couple them together quite hard (as do a lot of games and settings), but they can also be more decoupled. For instance, Ravenloft (the setting) is tied very very heavily to one set of feel/genre/scenario. On the other hand, you could (although probably best not with D&D) run a romantic comedy game set in Waterdeep in the Forgotten Realms with no adventurers in sight.

As for examples, I don't have first-hand experience with PbtA, Blades, or Lady Blackbird, so I'm going off of what I've read about them, mainly on the forums. Dungeon World, as I understand it, puts quite hard limits on the types of scenarios you can pull off--you're basically locked into "delving through dark dungeons, with the real threat of loss and logistic concerns being omnipresent and characters not being 0 to hero". It wouldn't work very well for, say, a swashbuckling pirate game with more comedy and witticisms than monsters or a high-flying "us against the gods" planar scenario.

I think it is an interesting way to break them down, but to be fair based on what you wrote I think D&D moved from 20 to 40 a while ago. Far too many mechanics designed to support their core settings in my opinion to fit 20 now. But yes, I am sure there will be those who disagree.

For me, the big distinction between 5e D&D (for instance) and PF on this spectrum is the presence of a "hard" default setting in the core books. 3e had a bit of this as well--it's "default" made pretty strong assumptions about the settings. Not quite as tightly detailed as Golarion, however. PF, for better or worse, fair or not, is identified (maybe just in my mind) with Golarion, while D&D incorporates multiple "conforming" settings, each relatively different. Even Forgotten Realms differs from the presentation of the defaults outlined in the PHB/DMG/MM in many ways. For instance, default paladins don't need a god at all. FR paladins get their powers directly from specific gods and have alignment requirements. FR's cosmology is also slightly different (the World Tree, rather than the modified Great Wheel). Etc.

I run 5e D&D in a very non-standard world. And the mechanical changes I've had to make boil down to "you know, no creature has a default alignment. And anything that mechanically plays off of alignment...doesn't." Even though the planes themselves are pretty different and all the races have different lore (sometimes radically) and I've got a bunch of homebrew, you can use a stock race stat block just fine and all the core classes and 99.999% of the spells (there's one spell I don't allow for setting reasons, and that's from a much later splat) work fine.

I very well could be wrong, but I know that Starfinder (for instance) is heavily tied to the setting in core mechanical ways. Another example is 13th Age, where even though you can swap out the setting, it has some fairly important things that have to be recreated (relationships with the Icons being the thing that comes to mind). May just be my bias, but that feels more tightly bound than "standard" D&D to me.

[1] I mean, you can do pure free-form. But that's pushing the bounds for what counts as a system, just like the PF board game pushes the boundaries for what counts as a RPG on the other end.