The Digis are both quite magical. They’re just VERY well thought out. Some things are condensed and simplified, while still being highly flexible. There’s not really one magical thing about either of them, but rather how their features are distilled into something immediately accessible but still deep enough to allow intricate sounds and tunes.
One can get ideas into them almost instantly, before getting lost in a complex UI could potentially kill the creative flow off. But then, you can keep digging, diving, and refining to the point of a complete track that needs little else to be pretty much complete.
On the Digitakt specifically, you not only have a sampler, but a fairly flexible wave table synth, with minor granular ability on top of it.
All these things can be said of the other Elektrons to a degree, but I think they really nailed it with the Digis specifically.
Also, their limitations push one to playing and creating differently. More on the fly.
I’m someone that has programmed all of my music one sound and one note at a time for decades. The Digis got me playing music live, on the fly, and building a track while I play it. To the point that I haven’t really been able to go back to purely programming the way I once did.
I would definitely call them special instruments.