How the HELL someone develops a 'NEW' (essentially table layouts from the '90s) way of building layout with CSS and delivers this massive dump?

Why can't I make a div expand to fill the remainder space in this layout?

https://stackblitz.com/edit/...

Seriously... I need to wrap 10 divs inside each other to make a design behave correctly really like in the 90s? And the new kids on the block think this 'flexbox' is any good? Amazing sheeple... amazing. ADD MORE WRAPPERS!

align-self should JUST WORK in the example above... but hey... it does not.

I just want to be able to add/remove the sidebar and content, keeping the footer below and headers above.

It's amazing the ammount of shims required to do anything in development on the frontend.