I am disappointed though that the Court House is the only successful modern architecture in Austin...
This is a weird assertion. If you mean that it’s the only stereotypically modern large commercial building in the immediate downtown core west of Congress St between 3rd and 5th st, well, ok.
Austin has a massive residential modern scene, with regionally and nationally awarded architects, and the the commercial modernism tends more toward retail and entertainment/restaurant design, as well as public spaces and installations.
Court house aside, It’s also more informed by a regional vernacular that incorporates western, “hill country” and ranch/mcm materials and design - think Usonian, but updated and slicker. (The Austin Public Library by Lake Flato is a great example of this.) Heck, even the burger joints have a whimsical Jet Age aesthetic (PTerrys by Michael Hsu), and Ellsworth Kelly’s modernist chapel - his last work - was just opened up a couple of years ago.
Also, Dallas is the worst. Houston has 10x the cultural opportunities, San Antonio is sleepy as hell but at least has a distinct character, and Austin is the city everyone wants to be in.