It's mentioned in the same breath as Montreal-Mirabel airport, which sounded OK on paper but ended up as a notorious failure.
Washington Dulles Airport helped Northern Virginia evolve into the successful economic (semi-tech) sprawl that it's become. I doubt I would have gone to many tech meetings in Herndon, VA, or Vienna/Tysons Corner, VA, unless it was for Dulles. Assume Sydney will see the same development.
However, Dulles took 60 years to be served by public transportation.


Like the link that was never built for Montreal?
Yes, the Washington Metro connects directly to Washington Dulles International Airport (IAD) via the Silver Line. The extension opened on November 15, 2022, providing a direct rail link between the airport and downtown Washington, D.C.
Alternatively, National is perhaps the best-integrated major US airport into a transportation network.
The new Sydney airport is opening its metro line with the airport! Bravo!
Istanbul, Turkey's new airport (2019) was built in the boondocks NW of the city. In 2024, the new Metro Line opened, and I used public transportation to get to downtown Istanbul (old city). I left ski stuff at the airport (luggage storage at the entrance to the airport/metro station). The train link is a breeze; it took me 30-45 min in rush hour (vs 1-2 hours in traffic in Uber/Taxi), and it cost me a little more than $1 USD. My airport round-trip to a free 2-night hotel was $4.
Again, another plug for Turkish Airways (free hotel (1-2 nights) for intercontinental travelers, it's NOT the UAE/Qatar (no war or bombs), Istanbul is easily one of Europe's or Asia's Top 10 cities (Dubai is a shopping mall like Vegas), 2 FREE checked bags including skis, and big seats/pitch) If James were traveling Turkish Airways, he could have skis-boots as one bag, and then another checked bag, so 3 checked items - plus carry-on.