I was expecting to find lots of comments about how boring this Full Art was, but I guess I'm out of touch with what the average collector desires in a Full Art?
I've always been a fan of Full Art V's (I haven't collected any full art lower case ex's) with patterned backgrounds (Like Starmie V, Genesect V and Alolan Vulpix V), dynamic backgrounds (Like Origin Forme Dialga V, Stoutland V or Torkoal V), or vibrant backgrounds (Like Vikavolt V, Serperior V, or the aforementioned Starmie V and Origin Forme Dialga V).
Meanwhile, for Full Art EX's, I tend to favor a less vibrant yet nonetheless colorful pallet, like on Dragonite V or Umbreon V, whose backgrounds are, if anything, more detailed than those of V Full Arts. And then there's the Gengar EX Full Art. S-tier Full Art with one of the most unique backgrounds of all Full Arts, which is also an excellent lore tie-in to the set.
Given what I love about Full Art V's and Full Art EX's, Kyurem ex feels like it got the worst of both worlds. In terms of composition, the Full Art V it most closely resembles is Vikavolt V, but not only are all the colors muted, but they are all shades of blue and grey. That background color may have worked fine for Dragonite EX, but that Pokémon was a rich gold, and the background was broken up by details like speed lines and wind lines.
I guess people with a better respect for color theory just don't like the whimsical designs that have drawn me to Full Art V's. Which is not surprising, considering I am usually one of the last people to think something (especially a Pokemon card) looks tacky.