Welcome to the wonderful world of ARM and driver blobs. Half of the waiting time is waiting for Qualcomm to release a blob (and that's if they even want to), the other half is including it in your build, and eventually making your fork's changes if you want to do so. For every single SoC in your lineup. Then testing if they can support the new requirements of Android.

Apple would have the same problem if iOS was open source and distributable by anyone, their chips being able to be made by anyone. Once again, Apple has picked the easiest (and least open) path, so, yeah, they can upgrade easily.