"Responsive" web design
Once upon a time, web pages were built with simple HTML and CSS. Which is light on bandwidth, and easy for browsers to render.
An example - I have to submit meter readings for an online energy company. The page used to use a straight-forward HTML form, and I could fill out all the fields and click Submit. A little while ago, the whole site was replaced with one of these damn "responsive" designs, and now that simple form is overloaded with JS that changes it from a single page fill-and-submit into a 3 page fill-one-field and click NEXT time sink. All just to make it look very pretty (probably to serve some ads too, but I don't see those!).