You might think that I'd know better and stop caring about the design while prototyping, but I still can't help it work 4 times as long on the layout than the actual logic

I too suffer from this affliction. Let me know if you find a cure

CSS flexbox and grid will take a lot of the pain of CSS away. Raw CSS is a shit pile, it’s full of hidden rules, gotchas and traps and if you think stack overflow or any tutorial site will help you understand raw CSS, you will learn the hard way bc raw CSS is arcane magic reserved for the chosen ones. Anyone who can succeed with raw CSS on complicated projects is a trans dimensional superbeing in my book