I will say that each company is allowed to compete in their own way, and that there's more than one way to skin a cat.
As I mentioned earlier, Apple's whole selling point is in delivering integrated experiences. As such, I really see nothing wrong with Apple integrating their music streaming service into iOS on a system level, or making it available on all their devices. After all, there is no guarantee that Spotify would have done the same (supported all of Apple's devices and services), much less made it work properly even if Apple hadn't done anything. I still don't have a spotify app for my Apple TV.
It's the same logic as to why google maps is that good - because Google's entire business model is built around gathering data, which in turn gives it a structural advance. Something that Apple can never beat, and which it counters by making its own maps app the preinstalled default on all their devices.
I am also reminded of Google's own apps for iOS and long Google often takes to update them to support newer resolutions and the latest iOS features. Gmail till this day still doesn't support split-screen on my iPad, yet it's the only app I can use to access my school's email.
So at the end of the day, from a (admittedly somewhat biased) customer's perspective, I am not interested in seeing Apple being made to compete on a level footing as these competitors. Rather, I am in the Apple ecosystem precisely because I trust Apple to make these decisions for me. By doing this, Apple at least ensures a minimum degree of standard amongst its products. For example, one of the key selling points of the Apple Watch is that it allows you to stream music via cellular on the go. As such, it makes sense for Apple to not only control Apple Music, but that it spare no effort in integrating this service into their own devices so as to make the whole experience as seamless for its users as possible.
Rather than farm this responsibility out to Spotify who, as a third party, is free to screw Apple and its users (by extension) over any time they wish (I still remember the whole google maps fiasco) to extract bigger concessions from Apple.
At the end of the day, the safest hands are still Apple's own.