Deleting old version of Pages

On an iPad, the installation of Pages v15.4 would simply replace any prior Pages version. That is the case on my iPad Pro after updating to Pages v15.4. However, this is not the case on a Mac that has a Pages v14.4 or v14.5 application presence and then installing the current newer version (Pages v15.4 in the case of macOS 26 or later) from the Mac App Store. Different icons and containers.

If you have created substantial custom templates, or in Pages Settings > Auto-Correction Replacement symbols, neither of these entities are automatically migrated from Pages v14.* to the newer Pages v15.*. That will be a job for AppleScript, or manual labor. Simply dragging the older Pages application to the Trash does not remove these two categories that are still stored in your local Library.