I think you vastly underestimate how much plastic we use and how optimized it is.

The global production of new plastics is a few hundred million tons per year, not including textiles (elastan, nylon and anything polyester is plastic). Then we have a ton of different kinds of plastics, mixed with thousands of different other components, to get the right results. A producer of packaging machines once said their most complex machine is for wrapping cheese, as that were like 5 layers of different plastics with different functions. Masks and other PPE is also mostly just plastic, and one of the really resilient kind.

We can substitute a lot of plastic, or simply not use anything as a substitute in some cases (thinking of the image of peeled oranges in plastic containers here, thats a complete waste), but that is way harder to do than people like to think. There is another reason than just cost why we use plastics.