This isn't rocket science. Only one of the top 10 courses in the GD list (Sand Hills) comes from outside what Pat Mucci/GW call the "Classic Era"; only 10 in the top 30 and 27 in the top 60.
Holding climate, terrain, and the environment constant, either the architects of that time were that much better, clients had more money or different objectives, things didn't cost as much in relative terms, golf courses take long periods of time to mature and "earn respect", or there weren't as many regulatory impediments. Of these, I suspect that only the last two have significant impact.
Comparing the top 30 on the GD list to the second 30, the three criteria with the highest average variance are the most subjective (Memorability, Ambiance, and Aesthetics, 6.8% higher) and, in my opinion, the more dependent on regional factors, history, and demographics (44 are located in earlier developed areas). For me, the three are also of lesser importance in terms of playing the game of golf. Resistance to Scoring, Conditioning, Shot Values, and Design Variety show smaller differences (4.4% higher).
As alluded to earlier regarding cool weather grasses, of the top 60 courses, only one has greens grassed with something besides bent (Kiawah Ocean- paspalum). Texas' only course in GD's Top 60, holding the last spot, is Dallas National. It too has bent greens, three different zoysias for fairways, tees, and roughs, and some of the best topography in Texas. The soils were literally nonexistent and had to be hauled to the site. The wind blows and the environment is very rugged. Having played half of the courses on the major lists, I am at a loss that Dallas National is not held in higher regard. I know that some of the touring pros prefer Vaquero (west of the airport) because it is more representative of the courses they play on tour, particularly the less complicated green complexes. Maybe DN is just too hard for the raters.
BTW, when people say that Brook Hollow was built on sand, we are not really talking sand belt material. At best, it is a sandy loam with quite a bit of clay mixed in. It's been awhile, but I remember a red tint in the soil. None of Tillie's Texas courses hold a candle to his work at SFGC and near NYC. I doubt that he checked his talent at the border when he came here.