Maybe (?) that works for the super-elite echelon who don't really have to "job hunt", and who maintain a resume only as a formality. But for the other 95%+ of plebs who have to actively apply or work with recruiters... MS Word is the only game in town, like it or not.
I loved the idea behind JSON Resume (https://jsonresume.org) a year ago (i.e. separate the content from the styling, store the content in source control and track it or branch as needed, and apply the content to whichever template you like). But I didn't like the limited export capability... so I wrote Resume Fodder (https://resumefodder.com) as an open source alternative. I'd love to create more template options when I have time... pull requests welcomed!
The people behind these resume generators know that MS Word is what most people need, but choose not to support it because that would undercut their business model. The business model dream is for you to host your content on their server, so they can mine it and sell access and hopefully cut off a slice of LinkedIn's pie.
So be it, but I just don't think there is a viable business model there. LinkedIn is already LinkedIn... and I suspect that smaller rivals will run into the same wall as Diaspora, Ello, and all the other would-be Facebook replacements. I think that people who check out these resume generators REALLY are looking for... a resume generator! And if it doesn't let you save your resume in the format that most people demand, then it isn't particularly useful in the real world.