The list reminds me of when people refactor code and then just rename things. Ok, foo should've been called bar, but is that really a design mistake? The biggest design mistake for me is that it contains the letter C - it never should've been cascading. There's probably a need to resolve conflicting rules but it never should've been THE feature around which the language is designed. The precedence algorithm, the specificity etc. has been a source of endless bugs because you almost never know if somewhere somehow an outdated selector is messing everything up in a hidden place far away from what you're actually doing.
Instead the core features should've been simple ways to, well, style. From the beginning you should've been able to e.g. position vertically. There's a huge list of these issues where for a long time the simplest things were difficult and involved too much thought to get anything done. Granted things have improved, but the main issue I have is that standards like CSS should be more practice driven, e.g. what are the things I want to get done and how do I do that. Instead this is how you will override a selector as if that's the most important thing.