At home I use a couple of Harman Kardon Onyx speakers. You can couple two of them to have an even better surround experience but already one of them sounds better than the sound systems I experienced in VW, Hyundai, Ford, Tesla and Smart during the last couple of years. It may look a bit ugly to have bluetooth speakers laying around with charging cables etc. but sound-wise I’d see absolutely no problem.

In general, I doubt that the majority of car buyers have significant audiophile requirements. Of course, most of them want to listen to music or audiobooks but a ‘good enough’ solution should be fine for most if it saves you hundreds or thousands of bucks.