[nilliams]

The lower-level abstraction (raw CSS) vs the higher level (bootstrap's grid) is more flexible. It's not simpler though, which is why the abstraction is worth learning. With a grid framework, you can make changes at a common level of abstraction that your teammates will understand. Because I guarantee the way you'd implement the equivalent behaviour in raw CSS is not how I would, and now we have both styles in the codebase (complexity).

Also yet to meet one of these 'designers' that would rather change CSS than HTML. And logically ... you can't understand CSS without understanding HTML, so preferring to make the change in CSS is just an arbitrary decision.