I'm with you that AI is overhyped but your suggested feature is "per app volume mixers" like in Windows? What's the use case on a mobile phone to warrant the extra complexity?
An example I can think of is when you're listening to a podcast or music that has been recorded on low volume. Without a volume mixer you're forced to increase the general volume, resulting in overly 'loud' sound notifications from other apps.
That can be fixed with Garmin notification sound being treated as a notification sound.
Adding per app volume control is IMHO a really bad UX. It means there's a master volume and then per app volume is like a coefficient the app volume is multiplied by.
My car has its own volume control separate from the phone bluetooth volume and I hate the experience of having two volume knobs interacting with each other when all I want to do is to increase or decrese volume
The use-case is the exact same one that is on a desktop. System-wide setting for a comfortable max volume, application specific volume because different apps handle audio differently. Youtube videos are loud, voice chat is usually moderate, some recordings are quiet.
Samsung/OneUI has a good few addons like this. Ability for multiple apps to play sound is good too (same addon) and the ability to output different apps from different sound devices at the same time (built in)