I find carrot coriander soup too sweet
I find most carrot soups are too sweet and/or one-dimensional. It's not something I make but when it comes to other sweet root vegetable / winter squash soups I definitely prefer some heat to balance the sweet - thai red curry paste for example. And all soups need more salt than you think. In a restaurant they are probably using a very salty chicken broth in their soup, so making it at home with veggies only will not have the same results. If I were just trying to quickly doctor a carrot soup at home I might try a little fish sauce to add salt and umami. Or dump in some salsa verde for heat and acidity. Actually I love perking up bland soups :)
Try using some additional spices to balance out the sweetness of the carrots, maybe some ground cumin which is quite dry? Clasically you'd balance sweetness with acidity so a little lemon juice might work, perhaps even a stalk of lemongrass that was removed before serving?
The sweetness of the carrots themselves will have a big impact as well of course, as well as where in the season they're picked, I'd expect those picked late in season and left longer in the ground to be less sweet.
Hope this helps