They barely even understand it?? I think the biggest problem with CSS is the same problem plaguing C++ and other older languages. Cruft. If there was proper versioning and pieces of the language were deprecated in favor of modern techniques, it would remove a lot of ambiguity. Heck, if there was a built-in linter that warned you about common errors that would be a massive upgrade!
The only bad part about CSS is that there’s a dozen ways to do everything.
With that said, any developer telling you they hate it probably hasn’t worked with the “state of the art” in other UI development. Go work with WPF, UWP, QT, ImGui, JavaFX, Swing, or any of the dozens of other desktop UI frameworks. Then, try to make a moderately complex style and apply it to several elements. It’s a PITA. I too hated CSS… but then I worked with WPF and JavaFX and lots of those other frameworks: and they gave me a fresh dose of perspective.
I’ll gladly take the ability to do everything a dozen different ways over the inability to do anything that strays from the happy path in the framework I’m using.