It doesn't take a rocket scientist to see that since the advent of Mojave, Apple is trying desperately to get out from under the weight of the 2010-11 Radeon Macs by making them as inhospitable to use as possible. High Sierra is supposed to be supported by Apple for another year that means that Apple's own apps should support High Sierra for at least another year.

The Mac App Store has tons of third-party word processing applications for very little money, and as I posted above, the LibreOffice Suite is a free Office solution of applications. Microsoft now requires macOS High Sierra as the minimum operating system to install current Mac Office versions - because Microsoft is now tracking Apple's customary three-year sliding window of. Staying as current as your hardware permits with both operating system and Apple's Mac App Store applications is still important to obtaining applications. There is no hidden agenda going on to get you to purchase a new Mac. Occasionally, Apple will make the next operating system a requirement for installing Pages/Numbers/Keynote as those versions take advantage of features only found in that operating system, and to make those applications compatible with it.

Same story for all other Apple applications not installed by the operating system. 2013, Apple has only kept the current released version of Pages, Numbers, or Keynote in the Mac App Store.

Office for macos 10.13