HTML is by default: responsive, vector, and highly readable on any device.
If you find yourself writing Css that removes any of these three features, take a minute to stop and rethink its purpose. Ask yourself what problem could be so important that it's worth solving at the cost of universal access to your content & readability?
Css is not here to make our lives as developers easy. It's here to enhance the usability of the web for our users. Css should never limit usability.
When we write stylesheets that cascade, we should keep these simple points in mind.