I, for one, think the HTML API (as in, the interface presented to the programmer, not talking about any other API meaning here) couldn't be worse.
How many attributes do you need to enable to place two pictures side by side in vanilla CSS? Is that composable, would the same set of flags work for two paragraphs? What about two tables?
HTML/CSS was never designed for the web we have ended up with, and I don't see how flexbox and any newer standard is making developers lives anything but miserable.
I believe flexbox does actually work for those cases, assuming you set the images/paragraphs/tables to be block elements (or wrap them in divs)?
Flexbox and Grid seem to me like recognition that the existing CSS primitives were designed for laying out documents, and don't fit well for creating UIs.
How about layouts being broken because (funnily enough) web developers are desperate to use features such as grids and flexbox that make their jobs less painfully awful?
Presuming you're a developer - surely you can sympathise with the desire to get people to upgrade their browsers so that webdev's lives are made more pleasant?