Agreed. Using this on the i9 8-core 16" MBP and the thing just isn't fluid. Has anyone at Facebook even bothered testing this on computers people actually use? Like some 2015 Macbook Pro? Or a 2014 Macbook Air or whatever.
I wouldn't even want to know how it runs on those.
I've got a 2015 MBP. FB is pretty sluggish, and I wonder why. When you send someone a list of notifications, it's probably worth getting the data ready in case they click it. And the resource usage is pretty big as well.
The mobile app seems to be just fine though, perhaps they want to push people to use that.
I wouldn't even want to know how it runs on those.