The need to just copy and paste code that links to CDNs is why so many people don't take frontend development seriously.
It's really nice, and allows me to comment out the bits I don't want/need and customize the few things I want changed (noto/consolas for fonts) and reuse the variables/fonts where needed.
Foundation, iirc originally required ruby, when I already was using node/npm for a lot of things... the better sass support via npm came later.
Having the CDN link, or download with the js and css files is in my view a sign that you know what you're doing. Requiring me to use two package managers and a build tool that I didn't pick is uprofessionel.
I don't see the difference from Ubuntu forcing you to use APT or C++ applications forcing you to use Make.