So far so good with a bunch of new (to me) native CSS like variables and grid.
It's when I start getting into override management around responsive treatments, custom page styling, etc. that my stylesheets get unwieldy. Sass mixins always helped tame the complexity when I hit this stage, and I knew how to use them properly to avoid bloat.
I see that native mixins are proposed, but looks like not an option yet. May need Sass after all. https://blog.master.dev/thoughts-on-native-css-mixins/