I considered it but I'm not a big fan of headphones, I usually listen to music at home or in a car.
One of the most annoying situations was when I had a great podcast I wanted to share with someone on a long drive, pulled out the iPhone 7 to plug into their car stereo and.... new-ish car.... but AUX only.... no dongle..... never mind!
I believe Apple removed the headphone jack 5 or 10 years too early. Bluetooth is not that great, and it's also not that widespread. AUX is not a floppy or CD drive, it is everywhere and works great and allows for high quality audio, no troubleshooting, no compression, no hassle. The alternatives (dongle? Bluetooth?) is comparatively nowhere and does not work great.
Wait what? You forget the dongle but don't use headphones? How many different cars do you drive/how many aux cables do you use? Just keep the dongle on the cable.
Personally I bought Bluetooth headphones and that's it, imo people are being too dramatic about it.
Worse than radio? That's not what I have experienced.
I'm using a 1,5€ BK8000L module (http://www.electrodragon.com/w/BK8000L) that I soldered to my old stock autoradio, replacing the tape audio circuit, and the quality is much better than FM.
Sounds like you're connecting the device directly to the audio system. With a radio transmitter, you're broadcasting on an fm band that the car picks up via the fm tuner.
Of course if the person is willing to attach something to the car audio as you have, that's the best!
I'm not sure what you were suggesting before, then, when saying that a bluetooth transmitter is worse than radio... ah unless you were talking about some kind of device => bluetooth => fm => autoradio contraption?
I didn't think about that, yeah, but the OP said they had an AUX input, so quality should be good with a (even cheap) bluetooth adapter on that.