Apple is not forcing you to change hardware.
Microsoft decided that they would only support current versions of Microsoft 365, Office 2021 for Mac, or Office 2024 for Mac on the same last three operating systems as supported by Apple for updates. Each Fall, when Apple drops the oldest of the three supported operating systems for regular updates, Microsoft makes the same adjustment for MS Office support.
It is paragraph two and your current document interchange issues with newer versions of Office that would be the motivation to make a newer Mac purchase to stay current with Microsoft Office for Mac updates.
LibreOffice is a suite of free applications that are purposeful clones of Microsoft Office. It is pretty good software with regular updates in functionality but not 100% compatible with newer Microsoft Office features. The current LibreOffice suite supports macOS Catalina or later. That is bound to change going forward.