And my argument is if you as a state are seriously consider a nuclear strike, you have accepted that millions will die, but it's better to completely wipe out the other opponent. No amount of rationalization can resolve that level of existential threat. Poland saying "we can threaten to nuke Moscow" is enough of a justification for Russia to view Poland as an existential threat to wipe off the map.

Large countries, and especially large nuclear powers, have multiple cities where industries are distributed. This remains true in Russia, as most of their military manufacturing capabilities remain spread out across Omsk, Kazan, Novosibirsk, etc.

If you wish to scare a country from fighting a war with you, even conventional capabilities are enough to highlight the pain while also not reaching the threshold where a conflict becomes existential.

So no, it does not make sense for Poland or Germany to develop nuclear capabilities so late in modern world.