The shuttle reminds me of one of those awful software development projects which start with clear, simple goals, until all the "stakeholders" start wanting their pet feature and need to be appeased because they will bring more money to the table, and you end up with a bloated, over-engineered mess.
As I remember, it was supposed to be two vehicles: a people-mover and a "space truck". Budget cuts and general human stupidity turned the project into a single, crappy vehicle.
First prototype completed 100 days after the contract signed. In contrast it took decades to build the Eurofighter. Granted a more complex aircraft, but they didn't have CAD back then either.
Mustang vs Eurofighter isn't really a fair comparison in a number of ways.
The most important, I think, is that Mustang wasn't a government project, but one designed and built by a private company to meet an existing wartime need.
Eurofighter by contrast was a government job start to finish, built by three companies in three countries. Starting with a DNA like that delays and cost overruns are baked into the process.