"styling a background" is just an example - I admit it is a bad one (glad I don't work in frontend anymore). I will read about CSS Modules and the other stuff you mentioned.
Thank you.
I worked with Polymer-based components ~2 years ago (an eternity in frontend-land), and I want to share my biggest pain point: you may want to integrate a `<cool-carousel>`, but it does not "look right" in your design (eg white website, but the carousel has a black background). If the author did not set up CSS variables, you have to either try overriding stuff, or fork it.
This problem is why every organization (eg GE with Predix or Electronic Arts) had to create their own components, so they can share the same "art style"/design.
Can you share your experience about that?
[1] https://matomo.org/
[2] https://goaccess.io/