The cookie is the on-campus experience. College is not just about the chocolate chips. It's about all of that stuff that holds the chips together. College is more than a collection of classes. It's the experience of living away from home. It's the cookie dough of relationships with other humans and even faculty. College can be about clubs and other student groups. It's about studying with your peers. College is the whole cookie.
But wait! While we are talking about learning stuff, I have one more point to make. Don't think that you should acquire all of the skills and knowledge you need for your whole career during your time at school. You will always be learning new things, and there will always be new stuff to learn (no one learned about smartphones in the '80s). In fact, a college degree is not about job training. It's not. Really, it's not about that.Then what is the whole chocolate chip cookie about? It's about exploring who you are and learning things that might not directly relate to a particular field. College is about taking classes that might not have anything to do with work. Art history is a great class—even if you aren't going to work in a museum. Algebra should be taken by all students—even though you probably won't need it (most humans get by just fine without a solid math background). So really, the whole cookie is about becoming more mature as a human. It's about leveling up in the human race—and that is something that is difficult to do online (but surely not impossible).
I have no issue with these points. However, we can even go right down to the jugular with this one instead of invoking some esoteric plea for a well-rounded education and social skills. There are compelling evidence that online-only lessons are not as effective and efficient as in-person, in-class lessons, if the latter is done properly.
I will use the example of the effectiveness of peer-instruction method as introduced by Harvard's Eric Mazur. Here, he showed how active learning, instead of passive learning, can be significantly more effective for the students. In such cases, student-to-student interactions are a vital part of learning, with the instructor serving as a "guidance counselor".
This is not the only example where active learning is more favorable than passive learning. There have been other students that have show significant improvement in students' understanding and grasp of the material when they are actively engaged in the learning process. Active learning is something that hasn't been done and maybe can't be easily done with online lessons, and certainly not from simply watching or reading the material online.
So forget about honing your social skills or learning about art history. Even the subject matter that you wish to understand may be more difficult to comprehend when you do this by yourself in an online course. There are enough evidence to support this, and it is why you shouldn't be surprised if you struggle to understand the material that you are trying to learn by yourself.