Its magic and only works on creatures like the spell says. Didn't seem hard to justify to me.
That might or might not be something to give feedback on. From my reading, it SHOULD target everything, but what does that mean for objects – does it melt away that marble column in the middle of the room?
The text of the spell is nebulous. It says that a stream of acid eminates from you in a 30' x 5' line. And then it says each creature caught in that stream has to Dex save or get covered in acid.
The wording sounds like it covers everything in acid in that stream, and if you're a creature, you can try to make a Dex save to avoid it, or you can use your action to scrape or wash the acid off yourself or another creature.
Normally, if a spell only targets creatures, it would say something like, "a stream of acid eminates from you, targetting all creatures within a 30' x 5' line of your choice." Here, the stream's existence seems independent of the effect on creatures, and the spell doesn't say what it does to objects.