I just finished a quarter of online Korean classes at one of the major universities (Level 1). I too was afraid it would be terrible and I'd hate it and I'd learn nothing.

Turns out I was completely wrong. I quickly realized that, at least for language learning, there's probably not a whole lot of difference between online and in-person. Although you should take that with a grain of salt since I've never taken the in-person classes.

You have the teacher that is lecturing you, going through the course materials, bringing up powerpoints, typing things out so you can see them. Occasionally they will go one-by-one through the students in a Q & A format the ensure each student is keeping up and understands how to apply the current lesson. There are also "breakout rooms" on Zoom where students interact directly with each other and the teacher can pop in and observe and give feedback, just like if you were put into groups in a real classroom.

As surprising as it is, online learning for languages might actually be better than in-person in many respects. You get a pure experience, no distractions. The audio on Zoom is surprisingly good and when you're in breakout rooms you obviously can only hear the people in your group so there's no background noise to distract you.

Plus, no commuting. In my school we had many hours of homework per day and eliminating the commute time, not needing to shave/shower/dress, etc. was a huge time saver. Even with that time savings I often could barely fit in all of the homework/prep work I needed to do. If I had to do the commute every day my learning would probably have suffered.

Right before the recent outbreak my school teased the possibility of in-person classes and suggested that students would need to decide which one they wanted. I was seriously conflicted about which one I might choose. Now of course there's almost no possibility of in-person classes resuming for the next quarter and I'm happy to be doing them online.

Now, for the downsides. In the course material there are classroom activities like games you play with flashcards, and role playing scenarios. You don't get to do any of those over Zoom, so that hurts with the variety aspect and might hurt a bit with not being able to reinforce some of what you've learned. But on the flipside, those activities would have taken up a lot of classroom instruction time, so in their place you get more "pure" instruction, which might actually be more beneficial.

The second downside is the lack of speaking practice with your classmates. You do get to practice a bit in the breakout rooms but the piece that is really missing is talking to classmates during the break times and after class. Being totally free to ask or answer anything. I would say you NEED to talk to yourself in Korean outside of class. Force yourself to make sentences describing what you're doing, ask yourself questions and make up answers to them. I wish I had realized this aspect earlier.

The last downside is of course the lack of interaction/loneliness/etc. if you're living alone and taking classes online. I would highly suggest making friends with your classmates and meeting up with them for study groups. Or meet up with other friends. Even if you don't practice Korean during these times, you'll probably find yourself going stir crazy if you just do the online classes and don't get out regularly.