I learned CSS 20 years ago. My strong opinion is that it should be renamed Crappy Style Sheets, but that would take away from its primary fault, that it's cascading. As we learned in many other things, "inheritance" is not a great idea. Especially for something that gets applied globally, by a team of five people. "I will now adjust this thing over here, which will mess up everything my colleague is doing over there" is not a good feature. Its main feature is to give you complex rules how to overrule a certain rule. As a feature it's a a headache, when that's what you base everything around, it's bad. It gives you complex ways to target things, and over time it became even more complex. If you're a sane person, you've learned to avoid most of these otherwise you'll end up with .foo > .bar:nth-child(2n) ~ .baz . Then you will adjust that and come full circle to my argument, which is that it will break Mark's completely unrelated thing.
At the same time doing the simplest imaginable layout was a headache. I've done it, and it was interesting as in, this is a challenge and I am taking it head on, but it never should've been a challenge. Things have improved exponentially here, but it should've been the idea all along. Not how to cascade rules.
All other criticism, the syntax etc. is nitpicky and not important. As long as it's allowing you to do something useful without much fuss, I am ok with any syntax. But it didn't and it never did. Making a webpage layout should not be a full time job.