I think determined individuals could, but it's much harder without ready access to pre-designed course material (e.g. case studies) and a learned facilitator, ideally one who has a mix of hard won industry experience, academic/research rigour and is a great teacher to boot.

This doesn't come close to describing every single professor, but I imagine (albeit without any sources to back this up right now) that the ratio of such unicorn professors is higher at Tier 1 univerities vs. non-Tier 1.

Perhaps with a larger supply of determined students willing to tackle this on their own, this is the year where a larger number of focused case-study groups could be formed and sustained online.

I didn't get an MBA from HBS, but I did cross-register into a class there while getting a different degree. The classroom experience there is sui generis, and it definitely couldn't be translated into an online format without diminishing its value. It's not just a matter of transmitting and absorbing information. If I were an incoming MBA student, I'd defer a year rather than going online.

Online communities self-select and self-censor. A student with a contrary, incorrect, or controversial viewpoint in a classroom has a voice and can spark discussion given they operate with best intentions and have a decent instructor. They can be wrong one day, come in the next day and continue to speak. Such a user in an online community gets downvoted, muted, banned, ignored, hidden, or any of those things that keep the chamber full of its own echoes.

In theory these communities can exist online. In reality, the vast majority of online communities are not open to being a classroom setting.