You're dead wrong.
I've watched both Koufax and Houck pitch and can assure you that, once Koufax was able to command/control his pitches, he was unreal in a way that Houck could never be. His curve dropped like a rock and his fast ball rose like a rocket.
Moreover, in his last six seasons he pitched 255, 184, 311, 223, 335, and 323 innings with ERA's (in the same order, 1961-66) of 3.53, 2.54, 1.88, 1.74, 2.04, and 1.73. In those same 6 seasons he pitched, same order, 15, 11, 20, 15, 27, and 27 complete games. Same six seasons, he had 269, 216, 305, 223, 382, and 317 K's.
Do I need to remind you that, as recently as last year, there was doubt that Houck could face a batting order a third freaking time?
Koufax was 30 years old in his last season, 1966, and quit because the doctors insisted he must.
In his last two seasons, 1965 and 1966, Koufax received a cortisone shot and capsaicin-based capsolin rubbed into his shoulder and arm before every game. After each game, he soaked his arm in ice, but with a rubber sleeve to prevent frostbite. For pain he took empirin with codeine every night and sometimes during games.
He threw a perfect game on September 8, 1965. He threw 4 no-hitters. He twice struck out 18 in a single game. He was the first NL pitcher in 20 years to post an ERA under 2.00 and he did it 3 times. In 1963 and 1965 he was the World Series MVP.