The desktop environment (Pantheon) is installable in Ubuntu, though.
Once in a while you might end up with a messed up situation that might require some effort to fix.
It's trying really hard to imitate Apple – they even have these "Human Interface Guidelines" somewhere that read like some sort of Apple parody. In reality it's a fake, thin veneer of a user interface bolted onto a generic Linux distribution. Apple software may have their own faults. I think most of the whining is just boredom, but iTunes for example is definitely not the pinnacle of UI. But the beauty of macOS has always been in getting some things exactly right with the competence and attention of a master craftsman/woman. I'd name text rendering as an example, or sleep.
Elementary OS is made by people who think wearing a turtleneck makes them Steve Jobs, but they just don't get that you also have to throw a prototype or two at your CXOs from time to time :)
I don't think Linux on the desktop will benefit from such cloning. Just look at Open Office: a UI that perpetually felt four years out of date that probably took five times as many hours of work as the google docs that actually made Office unnecessary.
Ages ago I remember using a login client that allowed you to pick which desktop environment you wanted to use, but I'm not sure how to do it on Ubuntu... I guess I could google around for whatever command-line-and-text-editor-fu is required.
The only thing that becomes messy is that some applications might use Qt, others GTK, and the themes might be inconsistent. Fortunately there's a GTK engine for Qt and a Qt engine for GTK that allow you to have a more unified experience.
The menu also might end up with many applications and the preferred applications for each file type can be a bit hard to manage when you have multiple desktop environments installed.
It's a great way to try out new ones. I tried Ubuntu + Cinnamon before making the jump to Mint.