The equalizer is easily 20 years old, and is restricted to presets. Presets! A parametric EQ is the only thing that can make Apple's own Powerbeats Pro sound good. And for several golden years (despite lots of Apple's work against it) we had a really good jailbreak equalizer that worked with Apple Music. Eventually I just gave up on the whole thing. But I remember going out for trail runs with good sounding music without worrying about losing my earbuds.
This is one of several things I'm considering for an Apple Music client I'm writing (they are one of the few streaming services that actually allows such a complete level of API integration, via MusicKit). Apple Music as an app is pretty mediocre, but with a 3rd-party app you can add custom EQ profiles, and even detect the type of device when it connects over Bluetooth and apply the EQ profile automatically on the fly when it is connected, to add it to the DSP processing path.