This! I feel like everyone forgot about CSS Modules, while I think this is the cleanest and nicest solution to all CSS problems and doesn't make you cringe like CSSinJS or styled components and others.
CSS modules is pretty clean, but disagree that JSS/styled-components are "cringeworthy". They're very powerful, especially when combined with React component props - i.e. let's say when a component has a prop active, that when true we want to change the color on something. A traditional way to handle that would be by toggling some active class, however this creates coupling from the prop to a class, and then the style to that class as well. With styled-components, you can remove one step from that with the classes, one less thing to think about (the developer doesn't need to think what classes are needed with what props, and then what styles apply on those classes).