@Serracollector yeah, Leovold decks are definitely gaining ground, but I don't think they want this as much as other decks would? They already have Claims and Trygons which could be better for them (Claim having synergy with the high Snapcaster/JVP count, Trygon being more controlling but perhaps worse in a post-Ballista world)
My thinking is that the "artifacts come into play tapped" ability is most useful for decks that care about tempo, or have problems with Paradoxical Outcome, and right now Green decks care the least about tempo or Outcome. Leovold decks are very slow/controlling and probably have a better natural Outcome matchup than other blue decks, and Sylvan Mentor is probably the most controlling/least tempo-centric version of Gush.
If this card was in White, Eldrazi would get a gigantic bump against shops (synergy with Displacer? insane).
If this card was in Red, then Jeskai Mentor and particularly Delver would have an interesting way to race shops decks.
If this card was in Black (obviously it wouldn't be, but hypothetically), it would be the best artifact removal spell in the color, giving straight U/b combo decks an option it never had before.
If this card was Blue, then it would have all of the advantages of being in red/black/or green, except castable off of basic islands which would be insane.
That's all I meant when I said that green was the worst color for this card (though pretty obviously the correct color from a game-design perspective). I don't want this in any green decks right now. I would have wanted this in some nongreen decks.
If I were still seriously working on White Eldrazi I would be curious about trying this out with a green splash (in part because Horizon Canopy is such an insanely good card), but ultimately I don't think the Eldrazi vs Shops matchup is bad enough to hurt the manabase just to run a shops hate card. (and this isn't a good enough anti-Outcome card to splash just for that, either)