[mightybyte]

For awhile now I've felt that the CSS libraries like Bootstrap, Semantic UI, etc are never the "right" way to organize your markup and CSS for a large project. They're great for getting out something quick and dirty that looks decent. But once your project passes a certain scale (in size or time spent maintaining it), the balance shifts in favor of semantic markup and style in CSS using BEM or something similar as an organizational paradigm. The latter just doesn't seem conducive to off-the-shelf styles because semantic organization is different for every project.

Another way of thinking about it is that CSS libraries build infrastructure for universal reusable widgets. In the beginning of a project it makes sense to build your app by putting together these building blocks. But as time goes by and the app grows, you start to develop a layer of higher level UI abstractions that are specific to the domain of your app. And when that happens it is often in conjunction with some kind of a re-styling and the old universal building blocks are no longer what you want. I've seen multiple large frontend projects go through these phases, and am starting to see them as a natural evolution of frontend projects.