I think age and experience would be a factor. Advising some very young vs somebody very old and experienced.
The relationship of the person who you deemed incompetent. Meaning is there some self serving angle to motivating such intervention.
I guess I'm naturally against the idea that people need help making the right decisions in a relationship. It's there journey and were all free to fuck things up . Do people fall in love and marry the next day sure .....do I think that's stupid ...yes ....but thats true freedom. Who am I to say they can't. Hey I've made plenty of mistakes ....I'm paying off a big one right now ....nre had nothing to do with it....but it still is my mistake. What if someone at the time tried to stop me . I doubt that would have ended pleasant for either of us. Hopefully I'll learn from it.
Saving people from themselves ...where does it stop ? Just NRE.