Same, except my stereo has a 3.5mm in.

I have several pairs of Bluetooth headphones but still use the 3.5mm jack on my SE all the time, and I use a 3.5mm lightning adapter with my iPad Pro.

i have a chromecast audio on the stereo which i find more convenient to use anyway because you can keep using your phone like normal while the chromecast is running spotify. For rare cases where I need direct audio, Bluetooth audio receivers are also pretty cheap. I am not saying you don't have a valid point, but you make it sound like it's impossible or inconvenient which imo isn't true.