Yes — ⌘Q and ⌘W are standard macOS shortcuts. Apple documents ⌘Q for quitting the current app and ⌘W for closing the current window or tab. Apple: Mac keyboard shortcuts
I searched for reports of both shortcuts failing system-wide after macOS 27. I found reports of other shortcut-related issues, but I did not find an Apple document confirming a specific macOS 27 issue that disables both ⌘Q and ⌘W.
Since the problem occurs across applications, first check System Settings >> Keyboard >> Keyboard Shortcuts, particularly App Shortcuts, for any custom assignments involving ⌘Q or ⌘W.
Also check Modifier Keys to make sure the Command key is assigned normally.
If you have customized these settings, restoring the defaults is worth trying. Apple: Change keyboard shortcuts on Mac
Next, completely quit any third-party keyboard remapping or keyboard-utility software and test the shortcuts again.
If you use a remapper such as Karabiner-Elements, review its rules and Complex Modifications for anything involving Command, Q, or W.
It is also useful to check whether macOS is registering the individual keys correctly.
Open a simple text application and verify that Q and W produce the expected characters when pressed normally.
Then hold Command while pressing them. This does not test whether the shortcuts themselves are functioning, but it can help identify whether the issue is limited to the shortcut combinations.
Finally, open an application's menu and check whether Quit still displays ⌘Q and Close Window displays ⌘W.
If they do, macOS is still displaying those standard assignments. Apple: Mac keyboard shortcuts
If the shortcuts still do not work after these checks, testing them in a new macOS user account may help determine whether the behaviour is specific to your current user configuration.