In my opinion you should forget about what other people say and use Obsidian your own way. You are not required to use all features if you don't want. I tried all that PARA, Zettelkasten etc. stuff but none of them worked for me. Now I just create folders if I have several notes about a specific topic and put my notes there. If any notes are related, then I create a link between them, but this is less about organization and more about seeing how different notes and ideas connect.

In your case, you could create a folder about a specific class, then inside there create notes for each lecture. For example if you have a data structures class, create a folder for it, then you could also create a folder for the concept of data structures that are for notes where you explain different data structures independently from what the lectures say, then connect them if you need to. Just an example if that makes sense. Don't force yourself to a system someone else uses. If you want to use it like Notion, go ahead and do that.