This looks pretty narrow to me. As a general rule, I don't consider
Shatter effects that only deal with a single artifact to be playable. Artifacts are certainly very prevalent in the format, and show up in almost every deck.... but the vast majority of them are mana rocks. I suspect the number of non-mana artifacts that see play to be significantly lower, so just dealing with a single artifact is pretty niche. In general, I prefer my artifact removal to be more flexible - either hitting multiple targets (like
Vandalblast), or just being more flexible (like
Reclamation Sage). Blowing up an early Sol Ring or other mana rock can occasionally be worth it, but it really depends on how powerful the rock is, and is rarely a good choice lategame.
However, that's just talking about blowing them up. Stealing an artifact outright (in blue) is a bit of a different story. As I often call out, taking cards from your opponents often means that they lack synergy with your own deck. However, since almost every deck has mana rocks available, that doesn't really apply in this case - worst-case scenario, you steal a Signet and create a janky
Mwonvuli Acid-Moss. Which, while not a particularly exciting card, isn't a terrible floor - the ceiling is obviously much higher, ranging from taking an essential combo piece (which, admittedly, will probably not do much for you) to taking a
Blightsteel Colossus.
Still though, I don't know if I'd run
Steal Artifact. Four mana is somewhat expensive for an answer, and being limited to just artifacts still feels narrow.
Dack Fayden is a mana cheaper and also has some hefty upside in the form of looting, while
Blatant Thievery hits anything, and multiple opponents. However, the card I think I would be most likely to run over Steal Artifact is
Desertion - it does a similar job of stealing artifacts, but also hits creatures (and other spells in a pinch). There is some opportunity cost for having a timing restriction and not dealing with resolved spells, but I still feel like it would be worth it in this case, unless you're running a blue deck that isn't particularly friendly to countermagic (such as
Maelstrom Wanderer).
It's fine for a dedicated theft deck, I guess. Blue doesn't have a ton of answers to resolved artifacts.