How can I restore audio clarity on my iPhone after iOS 18 update?

After updating to iOS18 on my iPhone 15 Pro Max, audio quality through both speakers and Bluetooth is horrendous. I don’t know how to describe it other than it sounds “messy”. Lows are too loud, highs are too quiet. You can play “Strange Premonition” by Kiki Rockwell on Spotify for example, and not make out anything that she’s saying. It’s actually hard to hear any lyrics at all.

I also tested some songs I own on Apple Music with similarly disastrous results.

It seems like Apple Music EQ is now impacting all audio output, I don’t know if it’s related, but it’s hopefully unintended. No EQ settings make the audio quality bearable.

[Re-Titled by Moderator]