It could be more useful and configurable, but I don't find it useless.
I'm a bit of an app hoarder, so it's a good place to keep all the apps I rarely use, but don't want to delete. I could just dump them all on extra home pages and folders, but then I either have to expend a lot of time organizing them (often in ways I don't remember), or spend a lot of time finding them. The App Library offers some automatic organization, and at least a chance at finding them in the alphabetical list. It's better than nothing.
If you are super organized, or only have a couple dozen apps, it's not very useful. But in those cases it wouldn't really matter if it was the pinnacle of organizing tools. No one needs a library card stack to organize their magazine rack. Well, most people don't.