I think of it as too thick, and the proportions are opposite of each other. Soup is a liquid-base dish, often with some solids in it. Chili is a solids-based food that will have a bit of liquid added so it's not a straight up thick paste. Liquids are only a tiny part of what makes chili. A hundred different things out there have some kind of liquid added to them for one reason or another, but it doesn't make them soups. Soup is also usually considered a side, while chili isn't. I don't think most chefs or cooks consider it a soup.