The cognitive act of /making notes/ (actual notes) on paper delivered the majority of the benefit. I usually never actually looked at them again.
Similarly, when preparing printed sheets of notes on a topic later, the act of creating those notes (the closer to the exam the better) again forced the processing and short-term memory storage of the information and I //usually// didn't need them.
Ideally there would be a copy of any slides (including snapshots of the 'boards' every few min / just before erasure) and an audio transcript to aid in taking a lecture again, and maybe a historical Q and A session so that the average quality of questions about the material could accumulate higher/more beneficial for the students.
Why is your professor not writing down or recording this important information? At worst, 5 people per lecture should be transcribing and merging notes and sharing with everyone else, not 100 people per lecture.
> writing down what you hear makes you better understand
Yes, you should handwrite a copy of the book/notes/whatever, at an appropriate pace for you.
The best way to understand something is to have to explain it. Writing your own summarized notes is a light version of that.
Even if you don't use the notes afterward, they are still useful. Video is a very useful method, but then the video has to be edited, or do you get three simultaneous streams, one of the professor, the board and the powerpoint? Videos like on Udemy are made for the medium. Class is not made for video, and I wonder how productive those videos are.
And when you go to class, do you really go home and see the whole class on video once again? That's way too time consuming. The notes are a good summary, much faster. Yes and it is taking effort, exactly what is needed. It puts your mind to work.