An example: CSS preprocessors, like Sass en LESS. They can be incredibly useful and powerful tools for writing CSS, but they require knowledge of how box models, positioning, inheritance and specificity work. Limited understanding of these things can makes things worse if applied through a preprocessor (for instance, unintended nesting). Preprocessors provide power, but it is a kind of power that should be used wisely.
Bower is another example: it can help manage dependencies, and makes it very easy to add new dependencies. This may sound like an advantage, but it makes it too easy to bloat a codebase and complicate a project too soon. Whilst it was easy to add a CSS library through Bower, it is now hard to manage
<button> styles as the CSS library does overly specific styling that is hard to override.