Yes it’s a bad idea. Universities that interview tend to rank students on strict criteria so the process is fair, and they therefore have no wiggle room to respond to begging. Should every student that begs get a place - obviously the answer to that is no. And, consider, they may have rejected you because you came across as unprofessional in your interview in some way, so you don’t want to double down.
You’ve been given the email in the post above that the university has provided to request feedback. Write a calm, concise note requesting feedback and in this, as the previous poster suggested, you can state how keen you are on this course, that you’d like to apply again next year, and you’d appreciate any guidance they can give on how to improve your application and interview. Ask about clearing too.
Don’t mention anything you think you did wrong in the interview, you have no idea what they may have noticed or cared about, so don’t draw attention back to any bad elements, you may have had a great interview, but there were just more people that ranked higher than you this year.