There are loads of technologies that, despite being decades old, do not qualify. So, no, it’s not “primarily a function of time”. It absolutely is about the utility. We can only be in a position to judge utility when sufficient time has passed, and AI ain’t had enough time yet to prove its utility. Given enough time, it might prove as useful as electricity, or it might just sit alongside computer operating systems - never quite making it onto anyone’s “this changed the world” list, even if it has as much utility as an OS.