I'm "using" our interns for this. First task is to create a document where they're supposed to write down everything that seems odd, overly complicated or broken. Even though they're sometimes in their third semester only, this pretty much always brings up something that can be improved on the spot without refactoring a dozen components.
But also for all the things that were actually just a case of the intern being inexperienced or too naive it's great for them to go back to this document after three months and see how their understanding changed over time.
Seems like a fantastic exercise, with benefits both ways. In hindsight, this seems so simple and powerful that I wonder whether it's a commonly accepted onboarding exercise for new team members, especially junior ones. If not, it probably should become.