As a designer that works primarily with Rails devs on large-scale applications, I feel the pain of developers that need UI/UX/application designers and can't find/afford them (for personal projects, startups, etc).

Bootstrap fills that very interesting and apparent need in the web community. It feels like a coping mechanism for devs who can't find good design/frontend resources, so I don't have a personal need for it, but I hesitate to dismiss it entirely as I personally know many developers that wouldn't have anywhere to turn without a tool like Bootstrap.

That said, the author's attempt to push it forth as some sort of a framework for all web language is a bit much. The best UI and UX will always be at the service of what the specific website requires, not skinned out of a modular system.

But this knowledge/resource gap is a growing problem, and I don't see enough of the design community becoming aware of it and stepping up their game to make things like Bootstrap less necessary.