Individual consumers aren't the only customers of Starlink. It also will bring high-bandwidth low-latency connectivity to the entire globe once enough laser-linked satellites are up. Industry and militaries will be using it. Whether this is a net positive for the environment or otherwise remains to be seen.

Also, the point of Starlink is to fund SpaceX's goal of a methane rocket. Methane was chosen because it can be generated from atmospheric gases and solar power. The logistics around scaling it up remain to be solved, but once it is solved, rocket launches will be basically zero carbon.