After macOS Mojave, Apple's operating systems (Catalina and later) require 64-bit applications and do not support 32-bit versions. This does not apply to documents, just the applications. Older applications whether from Microsoft 365 or single-purchases (Office 2008/2011 for Mac) are incompatible with Catalina.
Shortly after Microsoft Ventura was released in Fall 2022, Microsoft then ceased support for new installations of Microsoft 365 (subscription) or single-purchase Office 2019/2021 on Catalina. Existing installations prior to the changes in the first sentence will continue to work on Catalina, just without product updates.
Your options on Catalina without Microsoft applications are:
- A subscription (or purchase) to Softmaker's Office 2021 for Mac. This application suite opens Microsoft documents in their native document format, and the application interface is quite close to the existing Microsoft appearance. Free trial available. Supported on macOS HIgh Sierra 10.13.6 thru Ventura 13.*.
- The free LibreOffice Suite is a deliberate clone of MS Office and has quite high document compatibility with Microsoft documents. There is a learning curve supported by PDF documentation.