To some degree that's the case. The Falcon 9/Dragon do very much get a benefit from modern technology. Better machine tools, high-speed digital communications and onboard computers, better material science, the ability to run computer simulations of different flight profiles or to model the operation of a rocket engine, etc. However, in another sense the Falcon 9/Dragon represent very primitive designs. Indeed, 1950s or 1960s designs even. A simple cylindrical 2 stage LOX/Kerosene booster in combination with a simple frustrum shaped manned capsule. These designs have heritage going all the way back to project Mercury.
Yeah, and guns are vastly more reliable than rockets or missiles, too. Sometimes old and simple is the way to have high reliability, sacrificing performance.
