I completely agree with you, the music app is god awful now, there's literally no point in using an iPhone (or iPad) as an iPod anymore. It's a terribly designed and laid-out app that sidelines your personal local collection in favor of Apple shoving their streaming service down everyone's throats.
As for the stock apps, certain ones such as Find My iPhone, Find My Friends, Podcasts, iBooks, etc. were once optional downloads found in the App Store before Apple decided to bake them into the OS so if they wanna start giving their customers the option to delete those 1st party apps, there's literally no excuse for them not to. As for pre-loaded apps such as Tips and the Apple Watch, they're either unnecessary or essentially an advertisement for a product not every single iPhone user is rushing out to buy.
When it comes to the quality of Apple's software, the most obvious flaws are in the UI and the overall performance of the OS. But one overlooked aspect is the fact that under Tim Cook, we've seen a lot more bloatware from Apple's latest software releases which Steve Jobs would be furious over.
When they do stuff like this, I really do feel like Apple is starting to become a bit more like Microsoft.