I would put a lot of it back onto the candidate as well, if you feel like you are in a feedback gathering mode, ask the interviewer during a face to face if they have any feedback on the projects you presented, or anything they thought could be improved. Even tying it back to the job description is a useful tactic. ex “I spent a lot of time learning Solidworks surfacing for this project, and I think that would be a really valuable skill for the handheld products you design”.
That kind of dialog shows you’re open to constructive criticism and it gives you a venue for feedback at the time the interviewer is already committed to spend with you (as long as you haven’t run long on your time slot). Lastly since it’s face to face, the interviewer has less to worry about something being misconstrued.
There are some candidates that are just awful though, and no amount of constructive feedback will be useful to their career. I had a woman show up a few years back with no portfolio because her laptop broke. She had no USB drive with a backup, no website, no links to other sites that might have featured her work, I literally sat there for 30 minutes going “So…tell me about these projects you did”. The only feedback I could have offered her is “you should have rescheduled or cancelled your interview if you were going to waste everyones time here today”.