You make it sound like Android is this one big pool, but it's really about five or six operating systems, each with successive release enjoying a slightly better set of APIs and services.
What's the adoption rate of Oreo? .5%?
The truth of the matter is that Tango was a train wreck because it required specialized hardware and getting two Android handset makers - desperate to differentiate themselves from their rivals - to put in the same hardware to create a common platform was doomed to fail, let alone getting every flagship maker out there to cooperate.
So Apple comes out with computationally intensive ARKit - but Android handsets don't have the oomph that the A series chips impart - so ARCore will be by necessity be a watered down version of *that*.
There is a rapidly developing gulf between the A-series devices and the SnapDragons/Exynos/Kirins which are pretty much based on stock ARM cores, and as that gap widens so will the gap between the types of high intensity computing tasks they can run.
Android users smirk and grin and brag about the "true multitasking" on Android, but don't seem to realize that that text editor and that weather app and all those other apps running in the background are sapping CPU power and memory from the frontmost task, whereas iOS concentrates their more powerful processors mainly on the app which has user focus, allowing for performance that seems almost miraculous.