This is of course what the "war" is about at its core - do we prefer to to sound OK everywhere, but not great anywhere, or do we prefer to sound great for some people, but be inaudible to others.
The right answer depends on the content, context and audience. The choice is with the content creator, not with YouTube, and for many content creators optimizing for people with bad speakers is the right choice. Lowering the volume is not going to make "shitty" compression unshitty.
If they can offer several different tiers of video quality, they could do the same with the audio. Imagine a set of options that not only offers audio versions optimized for great headphones or optimized for phone speakers in a public space, but educates the (interested) user about the difference!
The right answer depends on the content, context and audience. The choice is with the content creator, not with YouTube, and for many content creators optimizing for people with bad speakers is the right choice. Lowering the volume is not going to make "shitty" compression unshitty.