Which uni course/school/subjects cannot simply be self-learned?

Anything where the titles are protected by rules/laws/regulations/bodies.

You cannot self-learn medicine. I mean: you could but then you couldn't legally help anybody.

Social Interaction and Teamwork, while we like to think we can do everything ourselves, it's just not possible

This might depend on your view of the world.

As you state autodidactism, you might view knowledge as absolute and measurable. I'd posit it might not always be, and you'd miss some social aspect be that feedback to socially constructing knowledge - as well as obviously only construct knowledge within yourself and not within and among others which would be a social form of knowledge - you might not need a school for this, but by definition a form of social environment.

[Feedback as both (and also separately) an accelerant to individual learning, and choosing paths of interest, is a different thing, and perhaps also worth exploring.]

Learning is a process. Each of us uses a different process and gets a different result. Of course you can learn a lot of things by yourself and get some level of understanding of the subject. It’s just highly likely that the result is not good as you study in university where you got a lot of people to discuss and inspire.

Weightlifting

Self defense

First aid

Shop

The Engineering Communication course at my university had a public speaking requirement. Talking in front of a small group was difficult for a large percentage of students.

Senior projects (group work) where workload is- intentionally or unintentionally- asymmetrical.

I wouldn't want my cardiac surgeon to be purely self-learned (although, I'd take it as a positive signal if they have great curiosity, and are well-read).

I think there are some hands-on disciplines that you could learn properly on your own, but which you could never be the best in the world unless you learned from a master.

Think woodworking, martial arts? Many more I'm sure.

I don't think this will be a very big list, though. You should be able to learn almost anything these days. I don't feel inhibited by anything except the sheer depth of some topics, and lack of my own time. I pretty much feel like I can learn anything.

Almost any topic can benefit from a good instructor, though, especially if it's one-on-one. They can steer you better than you can steer yourself as a newbie.

Is there a purpose behind this question beyond curiosity?

I think medicine as a whole. Yes, the knowledge can be self-learned. But the practical application less so.