A sauce's thickness changes its role
The idea
A thick sauce stays with a food differently from a thin dressing. One may suit a dip bowl, while the other distributes more easily through a salad. Calling both a sauce does not make them interchangeable. Consider how you want the food and liquid to come together.
A practical next step
When adjusting a home recipe, change the consistency a little at a time and taste the result on the food it will accompany.