I was struck by this.My issue with “neotrad” as a design school is I view it as just design. If we look at the design taxonomies outlined by Tomas Härenstam that you translated in post #42, it can be split into two groups: those with “indie” mechanics and those without. The group of those without are all games based on past designs. That’s two flavors of D&D (modern and classic) and BRP-like sim games. Everything else is some flavor of “indie”-influenced game: neotrad, storygame, or co-narrator.
I actually think he’s looking at this the wrong way, and MDA is my tool for showing this. Take the D&D category. He includes Pathfinder in this category. As we know, Paizo redesigned Pathfinder quite significanlly for its second edition. It is mechanically incompatible. Is it still Pathfinder? Yes. I would argue that Pathfinder 2e has almost the same dynamics as Pathfiner 1e. That is how people can recognize it as still Pathfinder and how it can be used to play the same kinds of games. However, there is one exception: combat.
Paizo changed the dynamics of combat from PF1 to PF2. Unlike PF1, the combat mechanics actually do what they are intended to do. Combat is balanced, and the encounter-building works. You cannot build your way to success. You have to fight effectively as a team, leveraging your synergies and teamwork to create advantages you can exploit. This is a fundamentally different dynamic from PF1, and it is unsurprisingly a point of controversy. Those expecting PF2 combat to operate like PF1 combat are in for a rude surprise, and it eliminates (or at least greatly hampers) the ability to optimize a character to overcome challenges.
I would postulate that you can preserve a game’s dynamics while incorporating “indie” mechanics. PF2 has social conflict rules. You can use the VP subsystem to run a social conflict like you would in Blades in the Dark. D&D 4e can do this as a skill challenge. Even D&D 5e has a limited from of social conflict (the social interaction rules on pp. 244–255 of the DMG, which @Manbearcat has written here about using for that). TIBFs and Inspiration are arguably an “indie” mechanic (since it’s kind of like a poor man’s aspects and Fate currency). Don’t forget consequences resolution.
Would people put these games as indie games? No. Thomas himself includes D&D 4e in the D&D category. That’s because these games have the same dynamics (more or less) that they’ve always had. It’s just that the mechanics have changed, and some of those changes incorporate newer tech and design ideas. That is why I view “neotrad” design (as articulated here and by Thomas) as just design. It’s a just the current state of the art.
As I posted upthread, I'm groping towards an understanding of MDA. But to me, it seems that 4e skill challenges do change the dynamic of play - they change the capacity of the GM to manipulate "offscreen" fiction so as to make it the case that X happens next regardless of the outcome of the action resolution process. (This is one way of expressing the conflict/task resolution contrast.) Hence why @Manbearcat, I and some others have seen indie GM advice and GM-side techniques as helpful for 4e D&D (whereas these are largely irrelevant to AD&D and probably to 3E/PF1 as well).
I'd love to hear further thoughts from you on this.