There are lightweight alternatives to commonly-used libraries. Some do away with compatibility with old browsers, some are less bloated, and some just do less.
bulma – A modern CSS framework based on Flexbox
Picnic CSS ; this is very clean.
U.S. Web Design Standards is very thorough and nicely done.
Spectre.css - a Lightweight, Responsive and Modern CSS Framework.
Programming history leading resulting in “functional” CSS – CSS Utility Classes and “Separation of Concerns”
In defense of Functional CSS | Mike Crittenden’s Blog
TACHYONS - Css Toolkit is a “functional CSS” framework. looks very low-level. composable things. Probabaly not suitable for quick and easy copy-pasting.
Tailwind CSS - A Utility-First CSS Framework for Rapid UI Development. See Tailwind Builder via HN
stylelint – “A mighty, modern linter that helps you avoid errors and enforce conventions in your styles.”