Google, though, specifically introduced Project Treble for the exact purpose of making the hardware-dependent portions of Android separate from the rest of it. It worked so well that there are now custom ROMs in the form of one system image that runs on a wide variety of devices using different SoCs. Yet Google themselves act as if there are insurmountable difficulties in supporting old devices. No there are not. They act as if they still need Qualcomm to keep older devices up to date, but they don't.

If folks over at xda-developers could do it in their free time, Google could too — if they wanted.

But besides, Android is feature-complete. It's done as a product. There's nothing more to be added. You really only need security updates.