There are three things that waste SoC performance in modern mobile devices: over-engineered system UIs, 3D gacha games, and locally running LLMs.

All of these can drive old devices to be obsolete with new software, and most importantly, directly allow the OS software to abandon the old hardware. And it can also directly take away from the already excessive hardware performance, and then overconsume the battery.

And the last OS to make large-scale use of transparency was: Windows Aero