The game is just colorful and the graphic don't look deep yet because isn't finished. If you look the character/creatures models or faces, they are not cute. Most people like and isn't to much influenciable over graphics, likeing the different kinds there are. There are many games out there you can call 'cartoon', and if you don't feel confortable with that, you are the one restricted from enjoying many good games. A lot of fantasy games choose a colorful look and fit to it, the same thing isn't used for Space games; why? because they are inteded to feel magical, alive, beautifull and shine (not my foult if you feel gay from that, because I don't 
/jk ) and you can achieve that with a colorful (vivid) world, while a Space game is better if felt mysterious because the universe and the future are. Graphics are representative on how they want the player to feels.
Colorful graphics are more inviting; the most important thing about graphics tough, is the art style/designs. Do dragons look cool enough? (in the images that show the creatures, they are colorful like the theme, but they look more serious than in most games, like the crocodile for exemple). If you dislike a kind of graphic you'll just be the one very retricted, missing good games, with great gameplay, that is the most important thing. Graphics of a game are just a small component of it, its not smart to judge any game from it. And you be sure, Stardock team understands of art design, has their games did it fine from beggning and only improves.
I think its really good for exemple, the design of the city and castle interiors and that it expands, the dragons and the trees that have some "pink" ones mixed in (I guess to everything don't look to greeny). And has they want the battles to look like in that movies, anyone can expect some very cool animations. A graphics in a picture can be very different from when it is in motion.
Its not smart from anyone to say it is bad technically. In its simplicity and unfinished, the graphics are detailed and carefuly made. The fact anyone says it is bad is just based on a very personal opinion that might be understandable or because is someone who expect/depends to much of graphics and visuals, either will not help yourself in any way for games. No good professional designer would say that the graphics here are bad. But most people will find it just ok has it is now. It will be better. Also there is the people that let themselves get dumbed down from games with amazing graphics (technicaly speaking, like hard to do) but of commom or generic gameplay.
The most important thing about it, in my opinion, the design, is very nice till now. I like this image for exemple: https://www.elementalgame.com/Screenshots/Kingdom_Scott_City_1280.jpg.
Also depending on how good a game is, its looks do get better or worst. And aside from cartoon graphics, there are many other important things (maybe even more) like the animations. Get a simple stick game with very cool animation and effects, might look down on a picture and a game with a good picture, have clunk or limited moviments. Talking about a game visuals in general, its important to see it also in motion and finished.
I personaly like games with simple but well made detailed visuals. It don't remove the attention of the player especially for strategy games. If I think about playing a game like CivIV:Colonization (good and full graphics) on multiplayer, then think about the simplier/cleanier graphics of Elemental, I'd sure prefer the least. Some graphics might feel better and amazing earlier, but not so much after some time when you saw it to much (for a strategy game where you need to think sometimes and will be looking at it a lot). Graphics like that can be more tiresome, and less inviting (feel heavier) like I said earlier.
Its really nice to look at Elemental pictures, I think while in the map it will be most comparable with the one from ROTK XI , which have those very cool amazing artistic graphics, but instead not cartoon or so colorful has Elemental. It can feel like if hand made or 2D.
Sry english mistakes.
