Mac is infamously keyboardist not-friendly. However Intellij is AFAIK THE BEST Mac app at mitigating the pain. It is the only Mac app of which I am aware that allows using the Option/Alt key to access mnemonics directly from the Menu Bar without resorting to the "Access the Menu Bar" keystrokes beforehand.
Now I admit to being a frequent complainer about Intellij bugs / shortcomings. But the point is I keep coming back to IJ. Eclipse is not a competitor. Thanks for paying attention to these small details that are not all that easy to remember/explain when queried whey we have strong (positive) feelings for IJ - even given its various quirks.
BTW: accessing the Menu Items using Option/ALT does require a modification to the Mac keyboard settings: one needs to create a custom Input Source to disable "special characters" via Alt/Option. I will paste the contents of mine after I re-verify its correctness.
Actually it appears that the Mnemonics are not even using the Mac OS/X standard menu-ing. They appear to be using Java windowing primitives. Notice in the screenshot below that the menus that I have accessed via the ALT/OPTION key are "living" within the Intellij window frame - and not from the Top Menu Bar. This is FINE -works GREAT! (IOW please do not change (/break..) this behavior!)