Earlier quoted context omitted.
I'd argue that it's a great tool for companies that have paid designers on staff too. What it provides us is a consistent and predicable framework to lay out pages. Anyone can contribute because it's becoming a well known/understood tool to work with. I doubt that more than 1% of websites need such unique designs that Bootstrap is too limiting.
A company I used to work for did exactly that. Our in-house graphic designer took Bootstrap and customized the living snot out of it. We (the devs) could work from the standard Bootstrap docs but the end product looked nothing like stock Bootstrap. Not only does it give both devs and designers a point of reference for communication, it makes it much easier to ramp up new devs since they don't need to learn the idioms…
I'd love to see an example of what the graphic designer was able to do with Bootstrapped HTML. Kind of like a 2013 CSS Zen Garden.