I actually think the engineering manager is probably in the wrong there, because if killer feature X is that critical to sales, then it needs to be prioritized in among the tech debt. It doesn't matter that the codebase health is not great if sales plummet. Being a good employee means sometimes prioritizing the health of the business and not the ergonomics of the work environment. And being a good manager means understanding when the health of the business is really at stake or whether the sales team is just throwing shade because they don't want to sell what the company has.