Word in Office 2016 for Mac was deliberately written to be more compatible with PC Word 2013. Mac ownership does not require the use of Pages.
There are no built-in lowercase capabilities in any Pages product, old or new. As I mentioned, one can create a new paragraph or character style that provides lowercase capability. One can write an automator service, that transforms a passed word or string of words to lowercase. An Automator service can be tied to its own unique shortcut key(s).
The free WordService collection of services in the OS X App Store has a service item for Lowercase. This would first need to be enabled in the System Preferences : Keyboard : Shortcuts : Services panel following the download/install — before it would work from the Pages application menu : Services : WordService: Lowercase menu structure. This WordService item has a keyboard shortcut already configured for shift+command+L.