To make taco soup less spicy you can dilute the taco soup by adding some chicken stock or other broth.
The more diluted the taco soup is the less spicy the taco soup will be.
If you're making homemade taco soup you should add less spices to the taco soup which will make the taco soup turn out less spicy as well.
When you need to make your taco soup less spicy whether it be homemade taco soup or already made taco soup you can make the taco soup less spicy by simply adding more of the original base liquid, such as more stock or tomatoes.
Some people enjoy the taco soup being really spicy while others find it too spicy.
I love my taco soup really spicy when I am congested or have the flu or cold but when I simply want taco soup the taco soup can sometimes be too spicy.
So I dilute the taco soup with some chicken stock but you can use beef stock as well depending on what flavor you want the taco soup to be.