Nope, that is a vacuous statement. Some people contribute more, some people contribute less - again, trivial to demonstrate, let's say I contribute X to others' QoL, positive or negative. If I go out now and throw my trash away in the park, I now contribute less than X, whatever X was.
> You seem to think having a low quality of life and lowering the quality of life are the same, and additionally, that improving the quality of life in a given state is something that a state, almost by definition, cannot do.
Where did you derive that from? To be fair I don't even understand anymore what you mean by quality of life :) Wikipedia: "Quality of life (QOL), according to Britannica, is the degree to which an individual is healthy, comfortable, and able to participate in or enjoy life events". QoL for the state is thus a metric (an average/median/...) of individual QoLs in that state. Within the state, individuals and groups (including the govt i.e. the state) can improve various aspects on QoL, usually via specific amenities (physical or "cultural" like safety/trust/...). They can also detract from it. Everything I said above follows from that.