Devs want composable blocks and design is all about context & harmony, so padding/margin depend on the context, eg I want a flex gap and not margins on elements. Without flex you had to do hacks, like negative margins on the parent row. CSS also doesn't have constraints or relative measurements. For example flex containers without a width can't have equally sized children https://codepen.io/brettdonald/pen/oRpORG). And this is a common theme, you can't elegantly style things based on existing dimensions, number of elements, etc which then you need to work around with media queries or hacks. Also, flex & grid have the same problem as async in JS, when you start building your layout with it, it's turtles all the way down, everything becomes flexbox or grid. That's what I think people complain about, instead of having tools that solve the few dozen common scenarios, CSS gives us thousands of rules that need to be carefully assembled and still not solve the standard layouts.