xCode is walled garden specific. If you're developing for Apple products it might make sense to use Apple products that will be designed to make developing for Apple products easier. I don't see how this is a "plus" to any developer who isn't developing for Apple products. There are plenty of devs who don't work on code related to Apple products at all!
Similarly, iOS integration is moot. What if they use Android? Don't need awesome iOS integration if you don't wall yourself off into Apple's garden.
I like polishing my own interface because I absolutely detest the design of Mac. That's a flavor and is not "factually" better. Many of the design decisions from Apple make me scratch my head in confusion.
That's awesome you enjoy that, but I'm not one to waste my time polishing, and modifying the OS I'm using. That's just insane to me.
One little side mention, the font rendering on Mac is so much more enjoyable to look at, that it impacts me immensely. Especially when dealing with web sites. Looking at them on Windows or Linux is horrific.
sjtgraham (https://news.ycombinator.com/item?id=13383982) and several of his or her peers find that it does have what they need, while obviously you don't. I doubt that there's an objective, correct answer to "does Linux compete with macOS?", but, if there is, I also doubt that we're going to find it by this sort of anecdote-slinging.