Not stuff like shadcn and Tailwind Catalyst, but a proper versioned, tightly coupled UI library with rich theming capabilities made for the 99% of users who aren't skilled enough at design to be cobbling together their own design systems or editing a Button component directly.
Instead they rode the wave (despite being best positioned to redirect the wave) and they're paying the price.
If it wasn't AI it'd be the first version of MUI that moves on from Material Design 2 as a default. Or Hero UI v3. Or literally anyone who brings sanity back to the space of component libraries and leaves "copy and paste code snippets" behind