All very interesting information, thank you.

Personally, I can speak for romance languages and English because those are the ones I currently speak abd have an insight on their culture.

English is the least formal in pronouns, but this only shifts the burden of formality to the whole rest of the phrase with specific verbs or constructions preference in a formal setting, which adds subtlety and nuance but also makes it harder to master than, say, French where it's a pretty straightforward distinction, though of course you still have to modulate your tone and language to a certain degree.

Spanish is nore forgiving than French linguistically, not as much culturally as you can still feel the old dons culture of respect in lots of Spanish speaking countries, so you need to tread carefully with your language and mostly with your actions so as not to be rude.

Italian is kind of a mixed bag. The distinction used to be very similar to French with "tu" being informal "you", and "voi" being formal "you". It's very old fashioned though as nowadays people use "lei", 3rd person pronoun, to express formal "you". I'd say most of the rules you mentioned in German culture apply to Italian culture too. There's generally a shift to more informal language, but in business, bureaucracy, university, government, and anything professional really, you're strongly advised to be formal. Good etiquette suggests you refer formally to older people and superiors, strangers too, especially the older you are. Older people tend to be much more formal and keep it that way until they have a close relationship with the person they're speaking to, though back in the days they would never have shifted to informal language even in this case. If you're on the younger end, you generally should never switch to formal language unless prompted by the older person. Younger generations tend to forgo most formal rules apart from the basics, and this contributes to generational divide as older generations think poorly of this kind behaviour.

Personally, I too think people shouldn't just jump to informal as hastily and unprompted as they do, not because I'm keen on social hierarchies based on age, merit, or career. I just think specific settings require a certain behaviour, composure, and decorum. And as someone generally distrustful of others and keen on his personal space, I'm also not fond of the implication of closeness informal language has.