The 747 went from concept to first flight in 28 months. How long did the Dreamliner take? YEARS. It isn’t just the government. We have forgotten how to “make” things.
While the 747 was designed and built in 28 months, it took another five years for the plane to finally mature to decent reliability with the 747-200B models powered by better high-bypass engines (later Pratt & Whitney JT9D models, General Electric CF6-50/80 models and Rolls-Royce RB.211-524 models).