The range is short for Thorn Whip, and its effect doesn't drag them far, so its ability to control the battlefield is limited. I did use it on a couple of occasions to drag a unit into a hostile area effect, but never to do anything too interesting. In this game, the cantrip does serve as a ranged attack for a class that has none of the ranged weapons its proficient in implemented yet though. But, Produce Flame is better for that purpose, hands down. Maybe someone else has had better luck with it.
Agreed, I think you really nailed the core of the problem. Druids - as currently implemented - are weak on Ranged attacks. Slings are not in game yet, and they are not proficient in bows and crossbows unless they choose elf.
Thorn Whip is fun, but underwhelming because of the short range. Produce Flame is the better ranged attack, and Shillelagh, and Guidance are essential Cantrips - and you will only have 3 of them until the game fully releases due to the level cap.
