As you have discovered, iOS/iPadOS does not provide the means to set a “default” mapping App where multiple mapping products are installed.
As is, other than installed web browser Apps (e.g., Safari, Firefox, Chrome etc.) - and passcode/credential managers (e.g., Apple Keychain, Microsoft Authenticator, Google Authenticator etc.) - where you can set your preferred default provider, you cannot set default alternatives for many other functions - such as your Calendar.
Apple does invite submission of comments and feature requests via its Product Feedback portal. If there are specific functions or enhancements that you might like to see considered for future versions of iOS/iPadOS, this would be the most appropriate channel through which to make these known to Apple. For iPad and iPadOS:
Feedback - iPad - Apple