So. Currently when you cast Dancing Lights, it counts as an ally despite being totally harmless and, as such, imposes disadvantage on enemy ranged attacks if adjacent to them. This is probably a bug.
However, I propose that perhaps we leave this bug in as a happy accident. My arguments in favor are twofold:
1) In the pen and paper version of 5E, dancing lights has an alternate application wherein it can be used to create a humanoid figure for distracting enemies. That really isn't something that can easily be done in this version of the game - however the archer distracting function is similar enough that it fills an equivalent niche, especially since enemies frequently just harmlessly walk away from dancing lights anyway.
2) Light has a much higher value in this game than in most tabletop campaigns, as we all know, and dancing lights often forces a wizard to spend his concentration - a valuable resource he could be applying to more potent spells - simply to see. This benefit of dancing lights makes that cost slightly less onerous, in my opinion, and turns it into an excellent cantrip rather than something one feels forced to take to participate in combat.