Media queries shape and form a web page to display on multiple screen sizes. That’s the core of responsive web design. Users can maintain the same level of experience that they get on the desktop even when they switch to a smaller device. The theory of responsive web design is great, but it’s not a silver bullet. When real world constraints and use cases arise it makes responsive design a bit trickier.
One of the biggest issues that arises is page weight. As Jason Grigsby has said, “we’ve remade the Internet in our own image, which, in the United States, is obese.” Having traditionally relied on the connectivity that ethernet on desktop computers provides, you could sneak by with these bulked up pages. Once you try to send these large pages through the tiny pipes to the tinier screens, page load becomes a major issue for mobile users.
Performance improvements can be made across the spectrum of design and development. The way responsive design is implemented fundamentally changes traditional design and development practices. Since you can’t comp or wireframe every breakpoint, it causes designers and developers to work more closely together. Even working in tandem in some instances to test and evaluate how the design will adapt as it’s resized.