Unless I'm massively misunderstanding your setup, that Docker image contains an entire OS and runtime, not just your website. Reasonable people can disagree about whether that entire paradigm is sensible but, having chosen to use Docker, complaining about image size in this way seems an odd choice. More to this point, most of what is in the image will be little to do with Node or its build systems..

That sounds like you are bundling the whole node_modules directory. Have you looked into Alpine based images and vendoring js dependencies into a bundle? 1 GB seems too large even for nodejs.