The time of CSS frameworks has really come and gone. There were four use cases, and all of those are more and more obsolete:

- "The Grid", which at this point has migrated to the browsers with Flexbox and (soon) Flex Grids

- A pretty skin replacing the browsers' default rendering of elements. These have improved, albeit only slightly. CSS has also become easier and you can easily do this yourself in 50 lines or so

- Fixing browser bugs/inconsistencies, which have diminished to a fraction of where we used to be

- "Components", which may the last remaining use case, but which have also become much easier to do yourself due to sane grid layouts