I onboarded a junior (not an intern though) as an otherwise solo engineer, and there definitely is something different about both being able to explain to them in such as way that they start to understand, and also watching them grow. I find it fulfilling, something that I don't think can be replicated with AI (and also good for everyone in sharing experience). Maybe it helps that the junior is very interested in the job and growing.

That being said, there's also a lot of time in teaching and explaining that isn't directly pushing work forward, so there's that to consider.