That's a pretty disingenuous argument. A universal ban on all plastic is politically (and economically) impossible at this point. Pushing for individual initiatives to eliminate certain kinds of plastic waste are achievable goals that can help us move away from plastics.
If someone has a minor political position or runs a nonprofit with limited funds and they manage to get plastic drinking straws banned in their municipality, they've done a small good. Changing the world for the better, even if it's in such a tiny way that it doesn't change the grand scheme of things, is both laudable and more than most people do. Regardless, the goal isn't to just ban plastic straws in one small town. The goal is to ban plastic straws and then move on to the next thing. The goal is to motivate other towns to also ban plastic straws.
One of the most important things about legislating plastic alternatives to common items is that it creates a market for those sustainable alternatives. And the more those sustainable alternatives are produced, the cheaper they get and the more viable they become even in places where there isn't a plastic ban. It also works the other way—the more consumers become used to using plastic alternatives (and form a negative view of plastics), the more demand there will be for those alternatives. Strategically, drinking straws are a great place to start because they are commonplace, easy to legislate/enforce, and alternatives already exist.
The idea that "Green people" only care about their goals if they try to achieve them with a hopeless moonshot is not a serious argument.