Honestly as someone who is looking for a junior role this could not be further from the truth. I just want to know how to improve so I can stop being unhappy at my current job and get a new one.
This has the implicit right answer: A job interview is the worst moment/place for feedback. There is just too much heart/animosity at stake on both sides.
I've been interviewing candidates for more than 15 years (for PhD /RA positions and then for Engineering) and every time I've given honest feedback, candidates just get into an argument on why they think the feedback does not apply to them...
It is just not worth it. If I want to know how am I at certain skills... I test myself in a less "charged" environment.
This could be true, and people probably believe it, but my experience stepping in towards the end of an interview and guiding candidates towards the solution was nearly always immediate counter arguments. "I was going to do that next!"