I think you underestimate your value to the company.

“All I do is copy code from the internal codebase and patch things together until they work” — this is exactly what established tech companies mostly need from their engineers. They want people with enough CS competence to not fuck things up while patching together new solutions from the institutional code soup that everyone knows how to navigate and review.

If you can do this reliably at 10% of your capacity and don’t have ambitions of applying creative solutions with unproven tech, you’re a real asset. Don’t leave rashly unless you’re genuinely bored or frustrated.