Big problem with evergreen standards: if you try to come back to a standard that is now twice as big but still has the same version number, there is nobody writing books to teach you what you missed out on. Want to come from CSS2 to 3? They got you. Want to do backend development for five years and then get a summary on what you missed? Go fuck yourself.
I'm not saying that this is a "bad" thing, but the last time I did any significant amount of frontend stuff was back in ~2014, and it was AngularJS, which was considered pretty ok at the time I think. I left that job and started doing almost exclusively backend stuff for several years, and when I looked back, the entire world had switched to React and transpiling JSX and a lot more CSS than I was familiar with.
It seemed pretty intimidating to try and pick that up again, so I never really left the backend stuff, and now I've managed to even avoid web stuff for awhile, because I kind of hate web programming.
Forgot that you can nest CSS now without Less or SCSS. Luckily my CSS has just barely tipped over into 'hot garbage' when I figured this out instead of in another four weeks.