It's much better on macOS, but still the UI quirks are there.
You can drag and drop songs from your library into the queue, but can't when browsing Apple Music. When in the (obvious) WebViews, you have to press those ellipsis buttons as if you're using a touch screen.
On top of that, they have the fastest SSDs in a laptop. It's not optimal, but swap is still extremely viable. Also, doesn't macOS have memory compression on top of that?
A lot of web applications perform really poorly on mobile and apps are made for that nice 'native' feeling. You also don't get push notifications or badges on the home screen. Mobile sites work for news sites and blogs, where you poll for content at your will, but for interactive applications, a mobile application that notifies you of interaction is a must in my opinion.
The desktop app is nothing special, just another web-view. Put Amazon or Google Music into Fluid and you have the same functionality minus media key control.
It took far too long to get an invitation, and you had to be 18 or older to use it. Facebook exploded first by being used by kids still in Elementary and High School. They initially cut out an absolutely major demographic, and people lost interest after a couple days.
You can drag and drop songs from your library into the queue, but can't when browsing Apple Music. When in the (obvious) WebViews, you have to press those ellipsis buttons as if you're using a touch screen.