Big notable ones:
* The menu tree.
* The keystrokes to access the commands in that menu tree.
The terminology. I do not have a meta key. You don't have a meta key, either. No new computer since the 1970s has a meta key. I'm a keyboard collector with a deep fondness for clicky mechanical keyboards; in daily use I use a keyboard from 1991. It predates USB and the "Windows" key. It doesn't have a meta key.
Here's the Wikipedia entry on CUA: https://en.wikipedia.org/wiki/IBM_Common_User_Access
Which, incidentally, I expanded from a stub about 18 years ago.
Another excellent piece of evidence that cua-mode is inadequate is that ErgoEmacs exists: https://ergoemacs.github.io/
It's actually not bad, but it's a total pig to try to install and configure unless you are already an Emacs guru.