To be fair there really isn’t that much plastic in space hardware, it tends to outgas and deposit itself on everything nearby in a vacuum. Some very specialized polymers sure, but not many, and not much.
It's turtles all the way down.
Space rockets just aren't prime examples of how plastics enable modern tech, of course it would be hard to find something that had zero plastic in the production chain, but food, medicine, and biology are really where the plastic shines and consumer goods are where there are lots of times where plastic is environmentally competitive to the alternatives unless your argument involves transitioning to a luddite society.