But that's entirely the point of Bootstrap.
It's not something that's supposed to be used by designers. It's perfectly tailored for someone like me: a back/middleware developer who sucks at design, but has enough sense to know that when I try to design something it looks like poop. It's for projects I can't afford to bring on a dedicated designer for. I can just include a single CSS file, follow a basic HTML structure, and have something that looks good enough on every browser and mobile device. It's not going to win any design awards, but again, that's entirely the point: without a lot of thought on the front end, I have a design that doesn't get in the way of what I'm actually building.
What would people like me be doing without Bootstrap?