I started to use it recently so I am not speaking for myself, but I have a friend who is a hardcore user that says that the key is that you must follow users who actually review content, and that it is specially interesting if these people have similar tastes to you. You can, for example, follow Martin Scorsese's user and you'll see his reviews.
I would actually like it better if they kept their social media functions separate from the lists (yes, I know private list is a thing). "Smart, funny" are not what I would use to describe it, since most people on Letterboxd think their one-liner reviews are way funnier than they actually are, and the signal-to-noise ratio is way worse compared to here.