They were already talking about “life unworthy of life” in 1939 though, although only those suffering from physical/mental handicaps back then, i.e. openly. And they pitched it to the public as being “your money” they were saving by not maintaining such people.
I agree, in hind-sight we can look back and see some early warning signs of what was to come during WWII.
But as of pre-war 1939, none of that had yet happened, and nobody then could fully imagine the Holocaust's future horrors.