* Group discussions in seminars. When you are in person, there's a better dynamic to holding a discussion. You can read others' body language and see when to speak up. Zoom works fine for very small groups (<7) but anything larger than that and it seems to get out of hand in my experience.
* Impromptu chats after class with professors to ask questions that I don't want to bug everyone else with. Same goes for chats during office hours.
* The opportunity to stumble upon events that you otherwise wouldn't have been exposed to. For example, I'm not muslim, but I attended a series of lectures on Islam aimed at Muslim students, put on by the Muslim student association. I learned a lot there and got to speak to fellow students and learn about their views and experiences firsthand. You're not gonna find an event like that online, and even if you did, you'd have to have filtered through all the other garbage on the internet to find it.
* Playing intramural broomball after pre-gaming with my friends. Aside from good memories, the social connections you make in college are very important and can help you a lot later in life. Many years later and it's great having a network of people in all sorts of industries.
* Living in a freshman dorm and getting exposed to people from many different backgrounds for the first time in my life. If you grew up in one place, then almost by definition, you didn't have much diversity in K-12.
You can't really replicate these remotely and in my mind, these sorts of things were half the value of college for me. And this is aside from the fact that I personally find it very hard to pay attention on a zoom lecture, especially if I'm sitting through 4 or 5 of them a day.