Semantic classes make sense for small and brochure-style websites. For any moderately complex website or web application, your class semantics quickly become a challenge. Naming things is exceptionally hard, especially when each "component" can have multiple variants each with their own modifier classes e.g. `alert alert-danger alert-with-icon alert-collapsible alert-expandable alert-hidable`. Multiply this by hundreds of components and you find yourself in class soup that's almost indistinguishable from Bootstrap and Tailwind. So I've given up on semantic naming because it's futile for ambitious projects.

Restyling a website without changing any of the markup is a pipe dream from the CSS Zen Garden days when websites were much simpler and more static. Apart from small/personal/static websites, it just never happens in practice today.