If you're interested in actually learning css, and don't just want to complain about how poorly written css is bad, this website is invaluable and provides concrete examples of how to build layouts and style elements.
You just need to actually understand the box object model and a handful of common gotchas.
How selectors are written has exponential performance implications. Using the wrong type of transform might make your page forego hardware acceleration, or use more battery on a mobile device.
At least typical programming languages are targeting a known set of environments and devices with known characteristics.
You definitely need to understand a lot more than the box model and a handful of gotchas.