Docs: remove mentions of deprecated .btn-primary and .btn-success

site/src/content/docs/customize/components.mdx

@@ -6,9 +6,9 @@ toc: true
 
 ## Base classes
 
-Bootstrap’s components are largely built with a base-modifier nomenclature. We group as many shared properties as possible into a base class, like `.btn`, and then group individual styles for each variant into modifier classes, like `.btn-primary` or `.btn-success`.
+Bootstrap components are typically built with composable classes: a shared base class, variant classes, and optional theme classes. For example, buttons can start from `.btn` and combine variant classes like `.btn-solid` or `.btn-outline` with theme classes like `.theme-primary` or `.theme-success`.
 
-To build our modifier classes, we use Sass’s `@each` loops to iterate over Sass maps. This is especially helpful for generating variants of a component from our `$theme-colors` nested map and creating responsive variants for each breakpoint. As you customize these Sass maps and recompile, you’ll automatically see your changes reflected in these loops.
+Many of these classes are generated with Sass `@each` loops over component maps (for things like variants and sizes) and theme maps. This keeps class APIs consistent across components and lets one map change update all related selectors at once, including responsive variants where applicable.
 
 Check out [our Sass maps and loops docs]([[docsref:/customize/sass#maps-and-loops]]) for how to customize these loops and extend Bootstrap’s base-modifier approach to your own code.