>When someone says HTML & CSS is terrible I ask them to design something better that lets you represent user interfaces that can adapt across multiple screen sizes, and allow complex layouts that Flexbox and CSS Grid makes possible. It is easy to criticize something if you don't have to worry how you would do it better.

Easy, something like Winforms or one of its successors like whatever they make Win10 apps in. Even the new Unity3D UI stuff is better.