Only what you need! Basic Settings and Styles to create UI-Elements for Websites and Apps. Less Code, less Size and that means Crispy CSS is simple and has less loading Time!
Youre are right, these Elements are not
There are many Frameworks that really great, but if you want customize them, that can be a lot of work. Crispy CSS is great to build Styles for Layouts that are unusual.
Crispy CSS uses BEM for naming, but a simpler approach of it. BEM is good to show other Developers what classes are belong to a Component.