Elaborating on this, both the YF-22 and the YF-23 matched and exceeded the requirements for the ATF competition. However, the design of the YF-23 was more "experimental" and the manufacturer wasn't able to prove that it could be mass produced by the deadline. For example, the neat ceramic tile design needed to keep the YF-23 engines from melting wasn't demonstrably mass produceable in time.
For a front-line fighter, the YF-19 was certainly less complex to manufacture since it didn't rely on bleeding edge technologies like the deformable wing, detachable limbs, QQR Inertial Vector system and the Brain-Direct systems. Furthermore, all that advanced technology only produced a plane that's at best marginally better than what the YF-19 offered. Even if the YF-21 had won, it would have had to undergo a redesign in order to remove the BDS and deformable wings, increasing time to delivery and cost.