For millions of years, nature has basically been getting by with just a few elements from the periodic table. Carbon, calcium, oxygen, hydrogen, nitrogen, phosphorus, silicon, sulfur, magnesium and potassium are the building blocks of almost all life on our planet (tree trunks, leaves, hairs, teeth, etc). However, to build the world of humans—including cities, health care products, railways, airplanes and their engines, computers, smartphones, and more—many more chemical elements are needed.
It depends on the context. Sometimes plastic is good for that, but in this case I don’t believe that it is.
Plastic is not a rigorous term. When discussing specific plastics it’s petty much always better to describe specifics, because plastics are too diverse of chemistry to do anything else.