Totally agree about the sound quality. Very flat, no compression where compression might be needed. I also have tuned in at times to their HD2 signal while driving and again the sound quality is below most of our standards. AM is worthless for music and even talk nowadays. I have a 2017 Mazda CX-5 with a great sound system, but the AM tuner is just about unlistenable. Case in point, driving home yesterday afternoon I tuned in to AM 830 to hear Roger Lodge (The Sports Lodge) and it was so bad I used my cell phone's Tune In app to listen to the broadcast in much better fidelity. Since many if not most cars don't even have a CD option in the sound system, can the elimination of AM be far behind? Maybe the FCC might not allow auto manufacturers to do that because of AM transmissions during a weather or natural catastrophe emergency might be considered necessary.
It's worse than that. Electric cars (Bolt, Leaf, Tesla) generate so much interference that their AM receivers are pretty much useless anyway. Even if the FCC were to mandate AM receivers, as the percentage of electric vehicles increases, the percentage of people getting decent reception will decrease. And, as you note---even with a good audio system like yours, the AM receiver is substandard.