I like how fast you can do stuff, but when when a designer creates something a bit custom it all falls part really quick.

I understand it solve the issue with reusability and style-guides, but for modern apps that would also mean everything should already be react componentized, so you shoudl not really care about css at that point idealy.

I rather use a mix styled-components (easily extendable if you need something custom) and css-variables for dark mode and defining global variables like colors,paddings etc. Plus I route-split so page only has it's related styles.