Is the problem of plastics one of producing too much or one of disposal? Only if plastics and other products that produced external costs expressed those costs in the price, can consumers use the marketplace to make choices based on self-interest. Instead, manufacturers have a discount paid by society to produce products that increase their profit but which eventually costs all of us. Wouldn't a person who believes in capitalism support the true price of a product or is the concept of a free market really about getting things "free"?
I imagine there is a plastics lobby that has a huge influence on Congress.  And since consumers see such an immediate advantage to plastics, few are willing to change the plastics paradigm. Plastic can take from 400 to 1,000 years to degrade and micro plastic is hidden in the gut of many animals, some of which we consume. When the impact of a product is hidden from the consumer, they cannot make an informed purchase, essential to capitalism.