Anecdotally, I've found Russians to be the frankest and corruption is rampant there, so I am not sure what the basis of your assertion is.
Politeness is about respecting others. You can communicate difficult things while still being polite.
And let’s not forget Korea. Korea where they have this little problem called “the highest suicide rate in the developed world.” And it’s no cake walk over there. Inequality is insane. What else would you expect from a place where people insanely ignore what is right in front of them for a little short-term gain?
Do frank, direct cultures like Denmark and the Netherlands suffer from these problems? You tell me.
And Russia? Are you kidding? They are completely a culture of respect. Everything is based on respect. It’s one of the most emotion-based societies in the developed world. They will happily overlook little niggling and inconvenient truths for the sake of respect or perceived virtue, as evidenced by their former system of government. Try learning something about Russia… I remember the founder of Scihub had a parasite named after her out of respect by an American biologist or something. She was super offended. Russia is perhaps one of the worst countries in that respect. Almost anything will upset a Russian, let alone the truth. It’s one of the most “never say anything even remotely offensive or else they will be upset” countries out there. The fact that you don’t know this really reflects poorly on your argument. You cite your “experience” but then don’t appear to have much.
And yes I realize she’s not Russian, there’s a huge amount of overlap in their cultures.