This is one of those things that your mother should have told you, but you probably weren't listening, anyway.
Makers of laundry detergent are in the business of selling their product and selling as much of their product as they possibly can. They recommend that you use a certain amount of laundry detergent in each load. it's printed right there on the box or bottle.
That recommended amount is a maximum, not a minimum. Here's why:
Laundry detergent takes dirt off your clothes because dirt sticks to the detergent, and then the detergent is washed away in the rinse cycle. The more detergent you use, the more will be left behind after rinsing. If you use too much, then your clothes will be permeated with laundry detergent and the dirt that is stuck to it.
I sometimes rewash the clothes that my daughter-in-law has already washed because they still look dirty. I use no detergent at all. The machine fills with suds in the wash cycle, and then it rinses out all that built-up, dirty detergent in the rinse cycle.
So remember, in the case of laundry detergent, more is not better.