I am a quite shy person ad often, when i find an interesting composition-subject (like a person doing something, a goup of people in a nice setting etc), i struggle to capture it because i feel like i’m being rude taking pictures without their approval, but at the same time i think that, by asking them, the spontaneity of the shot would be compromised. What’s your take about it?
Depends very heavily on whether there’s a reasonable expectation of privacy. There are almost no countries where taking a photo in a public place requires consent unless you’re violating a reasonable expectation of privacy, stalking or harassing them.
Posting is a different matter and varies more, but OP asked about taking photos rather than posting.