Methinks we have a different definition of the word “Fantastic” — I’ve always found CSS pre-processors to be an utter and complete waste of time, doing things you either can already do if you understand how to group selectors, decreasing code clarity with the whole mixin rubbish.
The last of those only exacerbated by how it pisses on any attempt to use a document inspector to reverse engineer where/when things go wrong, since the code you’re writing/editing in SASS bears zero resemblance to what’s actually deployed to the UA.
Much like the mind-numbingly dumbass trash that are HTML/CSS frameworks, it reeks more of propaganda exploiting people’s ignorance of how to use web technologies properly, than any form of actual aid in development.
At best they’re a salve for apathy and a balm for ignorance. At worst they are an outright scam promoted by people trying to prey upon that ignorance.