Unfortunately macOS Big Sur is the last supported version of macOS for a 2014 Mac.
You may be able to use the Microsoft online version through a third party web browser, but even many third party web browsers are now only supporting the three most current versions of macOS (currently 12.x, 13.x, 14.x)....those third party browsers may work for a while until the Internet changes enough to render them useless as well. Sometimes someone may backport changes of a current browser into a customized browser to run on unsupported operating systems. The online version of Office products are not quite the same as the stand alone apps, but should be Ok for basic stuff.
Or you can use a third party alternative such as LibreOffice.
Or get a newer computer....I know, not ideal since I do like to keep using older hardware as long as possible, but these days software developers are cutting off support for older hardware & software. Even Windows laptops are being forced to upgrade just to install Win11 these days.