Actually, if you research what happened in all of those other places versus what happened in Poland, the Poles got far the worst of if. The German occupation of Czechoslovakia was brutal and oppressive and they killed a lot of people. For having resisted the oppression in Poland was far more brutal still.
There is a sound military rational why the difference. You want to signal that resistance carries a much higher price than cooperation. This is a strategy that the Mongols demonstrated with brutal effectiveness, and the Third Reich were superb student's of the Mongols' methods. Occupiers always want to coopt the occupied. It ties down less force and increases value of the economic exploitation of the occupation which in many circumstances was the point of the exercise.
Except when they don't, and instead declare wars of extermination, and slaughter those who surrender wholesale. With the predictable consequence of getting their enemies to fight fanatically, and thus losing.
As for exploitation, Germany got more out of Russia and all of eastern Europe by trade prewar, than it ever managed to extract by wanton slaughter in the occupation. A few cameras and some electrical equipment readily bought a quarter of Ukraine's harvest. An occupying army that murdered millions cost more to send, and got no more out, ever. See Milward on the war economy figures.
Your revisionist excuse fantasies about rational Nazis are your own sordid delusions, not history.