Unfortunately your in no luck,
The choice is very simple:
You want a work-out watch : Garmin/Fitbit or any other that support spotify premium users/offline music that you paid.
If you prefer just the fun of the apple stuff without the work out portion... stay with your apple watch :) but even then its not easy for music :)
Now you will say: what if I pay itune officially.. well they even made it difficult for you to do that ... imagine after paying and paying still its not easy.
Look, you want a simple watch that is more precise for GPS and that allow you to use your "spotify premium that your already paying" my answer: Garmin forerunner 245, if your ready to pay as much as apple price then look for the super powerful garmin fenix series, you'll see, you'll get 1000% more and better precision if your goal is strictly work-out intelligent watch.
Again if your goal is to keep your apple Goodies keep your apple watch but for a real workout watch that doesn't block you because they offer them self a music paying service, get another watch... you'll feel better immediately :)
Thats my honest opinion after having purchased many iphones, 2 apple watches, even got an apple computer... and trying an itune subscription and still no luck... forget it its no win situation ... unless you want to open your windows and continue throwing money... someday they will make it easier but only for iTunes subscribers :)
Good Luck but trust me better to invest a 300-500$ CAD (or less in USD) and immediately get what you want.
bye bye Apple