I agree with you that I don't think aliens are actually creating crop circles here, but I think that would be an effective way for an alien to post an "I Was Here" sign and then leave us alone.

We're out in the boonies in the Orion arm, right, and compared to the age of the universe and how old some civilizations must be by now, we are relatively early in our evolution. Ergo, either the more advanced civilizations haven't bothered to come look for us because we're so far away, or they know we're here but figure we need more time to ourselves and we will come to meet them when we're ready. So let's say an alien comes to scope us out, just to see what's all up in here? An anthropologist alien, the academic type that doesn't care how long they have to travel as long as they get to see something interesting. A bigass crop circle would be like their parting gift, "I'll leave this for you to ponder, talk to you later" <3