I understand where you’re coming from better now, thanks for clarifying. I also realize I didn’t explain the core of my point well.
I think the real devil’s in the lists, not the core mechanics. That’s what often gets overlooked when people assume systems like GURPS or Savage Worlds are “easier” to adapt. Sure, they’re generic in theory, but in practice, you still have to wade through catalogs of traits, gear, abilities, and system-specific edge cases. Then you have to curate what actually fits your tone, genre, and setting. It sounds modular on paper, but the actual process can be just as involved as working from a non-generic chassis.
Some generic systems help by offering strong ready-to-play content, Savage Worlds and BRP do this well. GURPS choose poorly. Until products like Dungeon Fantasy or Monster Hunters came along, you were stuck deep in the catalog, building from scratch. So even in “generic” systems, you're often still doing heavy lifting unless you buy into a very specific supplement line.
D&D, even 5E (though not 4E), has fewer assumptions baked into the core than many people think. The base mechanics are straightforward; the genre flavor comes from the surrounding lists: classes, monsters, spell options, equipment. In that sense, it's structurally different from GURPS, but not inherently harder to adapt. Having rebuilt 5E for my Majestic Fantasy setting, I found the basic components very modular. Most classes/subclasses come down to five or six new features, and the mechanics slot together cleanly once you understand the internal logic.
That said, 5E does have its difficult points. The 20-level progression encourages far more development than most campaigns ever need, and the Warlock, while conceptually cool, feels like a dumping ground for kewl powers. But even so, the overall effort wasn’t significantly different from what I had to do when adapting GURPS 4e for a similar purpose back in the day.
Majestic Fantasy Rules for 5e
Also, I wouldn’t say Crawford’s approach is rare in the OSR anymore. He may have been an early standard-bearer, but over the last several years, more designers have embraced the same spirit, treating classic D&D mechanics as a toolkit rather than a script.