> Yet my recently hired collegue insists he spent more time learning from Youtube than from lectures at "proper" university.
Neither of these are likely to be ideal ways of learning.
From what I recall, research shows that people often believe they have learned a lot by watching a video, but when tested they are often unable to identify the key ideas they were being taught.
Students ideally need personal feedback and a direction to focus on. To be able to ask questions and interact with what they don't yet fully understand. To be listened to and understood.
Remote classrooms can be organised to match what happens in an effective classroom (here simplified): the teacher introduces the key learning goals and to set out some relevant tasks with examples, then walks around the classroom giving their time to students 1-1 while the other students work independently on their tasks (likely in a way that allows them to discuss their understanding with each other, with access to reference materials including the internet), and brings the class together as necessary and at the end of the session.
Being sat together in a Zoom call for an hour (or ultimately many hours a day) is not accurately reflecting what is really happening in a good classroom, except in the presentee-ism aspect.
MOOCs and, in general, sources of pure content are generally not personalised enough to engage most people beyond the first lecture. They can't predict what a student will need support with, and don't proactively act on this - whereas schoolteachers can and do. CS50x is an extremely high quality MOOC and only ~2% of registered students are destined to ever complete the semester's worth of work.
Reaching mastery best will involve using the resources we have in human teachers: teachers to guide learning.