Is the music. At least in the original anime:

Seriously, this song is lit. Way more people would play ramp on Arena if something this good played whenever you resolved an Ugin.

7354706
Yes, but do you really want to listen to a four-minute track every time someone plays Ugin? It's a bit of an apples-and-oranges comparison given the different media involved. I will say that in terms of in-game sound design, Hearthstone definitely does a better job than Magic. Which makes sense, since that was always part of the design rather than something added in decades later. Plus, Hearthstone has that vast catalogue of WoW music to draw from.

Still, one thing I will say in Magic's defense: When the trailer videos work, they really work.

7354915
Yeah, I know, comparisons to anime don't really work. And the Eldraine and War of the Spark trailers were both phenomenal. I mostly just wanted an excuse to share a great piece of music I stumbled upon.

7354706
Honestly, the song sounds fairly generic-jpop to me. If I threw together a long playlist of a hundred jpop songs and ran out of good ones, this would make decent filler I guess.

That said, the fact that it's associated with yu-gi-oh reduces the potential (minimal) enjoyment I could have for the song. If I forgot what the song was for in the above playlist (non-zero chance of that happening considering how little it stands out), it might stay in the playlist. But if it reminded me of yu-gi-oh each time it came up, I'd quickly delete it from the list and be happy with 99 songs until I found different filler.

I'll concede your main point. I can't think of a single MtG song. 0 is still less than this offering.