Apple wants to use a common foundation for both iOS and macOS. However, it was released way too early, and for the first time (at least in my experience) Apple deprecated several features without caring about compatibility. And to make things worse, lots of former features are now broken or not implemented at all, meaning that we had to add lots of workarounds or implement stuff on our own. And there’s still work left to be done.
OK, I get it, it's a nice thing to have to simply things. Here's the issue.
One, it gives more and more credence to the feeling of many that Apple simply as stopped caring about computer users vice iOS.
Two, when they did something similar to the iWork suite, they brought most of the features back fairly quickly, and it affected a side application, albeit a frequently used one, and not core functionality of the OS.