Politeness is absolutely necessary, and I hate seeing callous impoliteness in wider society (e.g. towards service workers).
I suspect I would severely struggle in a deeply polite society (stereo-typically Asian?). I can relax the most around very direct people (Dutch?).
I am continually stressed when dealing with anyone that absolutely needs politeness. Example 1: a very close friend who can be triggered by anything reminding them of their abusive ex. Example 2: a self-centred acquaintance that needs pandering (however isn't polite in return).
There's a balance - but it's hard to find. Perhaps I'm confusing two different dimensions, politeness and honesty?
Edit: This is a wishy-washy comment. Difficult topic, straight-jacketed conflict, interpersonal stuff that is hard to understand and talk about.
It is possible to be direct, honest, and polite.
You should consider the possibility that you're mistaken in linking "rude" with "direct"
They are certainly correlated so not orthogonal, its much harder to not be rude when you communicate a complaint than with praise.
You need to put much more effort in when you complain about something to not be seen as rude, that means they are not orthogonal. It also means many will just not do it since its too much work.
I could grant there is also an objective friction surface, a fourth scalar describing how difficult it is to be direct, honest, and polite at once.
‘Traditional’ etiquette books are actually pretty good at this stuff: one definition of etiquette is to never out another ill at ease or uncomfortable. Discomfort is contagious especially through body language, so the first thing you must do is be comfortable yourself with the feedback you’re giving.
For me, it stems from seeing when someone changes their behavior or words in a way that's no longer authentic to themselves. I like when people are real with me.
But being real or authentic also isn't an excuse to be a jerk.