Same here. Most of the devs I know who don't like CSS actually never read the docs, or really understand the box model and padding vs margin, etc. They don't treat it like a real language, and so they hate it. I've even worked with someone even recount that once they read the manual, it got a lot easier!
Of course, I'm a dinosaur. I still don't know nearly as much about flex, CSS grids, etc. but i actually have very few cases where the CSS that worked 10 years ago doesn't work today. Flex just makes it much easier, at the cost of adding multiple ways to do the same thing. IMO there's a real cost there. I try to use it minimally, but newer devs like to start with flex first.
I understand the box model well and I still hate CSS. I just feel like CSS has way too many unique things to remember that have no apparent logic to them.
Of course, I'm a dinosaur. I still don't know nearly as much about flex, CSS grids, etc. but i actually have very few cases where the CSS that worked 10 years ago doesn't work today. Flex just makes it much easier, at the cost of adding multiple ways to do the same thing. IMO there's a real cost there. I try to use it minimally, but newer devs like to start with flex first.