That was true a couple of years ago, but healthcare.gov was a wakeup call, and everybody from the president on down takes reforming government IT seriously.
I was part of the healthcare.gov "tech surge" and I can tell you firsthand that the government is willing to change. In the last year, the healthcare.gov UI was streamlined from 76 to 16 screens for the average user. Large parts of the site now run on AWS and more is moving. The most problematic individual component, the login system, was rewritten from scratch with an API-compatible, drop-in replacement which now serves 100% of traffic. And this has been done within the same agency responsible for the original site. It is not a story of "smart hackers" parachuting in and wresting control away from government bureaucrats, but rather partnering with the agencies and creating reform from within.
USDS itself, although started by the White House, now has bipartisan support and a real budget to grow. Although you are right that there are powerful entrenched interests in the beltway, the political will to change is there, and now the challenge is to recruit people like Andrew to seize the opportunity.