I've spent a good part of my career doing tooling for developers and customer service. The amount of "customers" is a lot smaller and they tend to be technically proficient and know what they want and need.
Eh. It can become a bad job too. When a tooling team has fulfilled its basic mission and things are good enough it can turn into a really bad job because it turns into a scrum death-march for features of questionable value and never ending bug fixes to fill time.
Your "customer" for a framework is a fellow dev. That can make all the difference in the world. Design and marketing generally take a back seat.