Both the IAP and ad plugins are maintained and should be up-to-date
It is a bit surprisingly to read this statement to be honest.
Regarding IAP. There has been bug fixes for the Google Billing Library in v3.0.1 (released 2020-09-30) and also in v3.0.3 (released 2021-03-12) which both could affect cordova builds afaik. The Scirra IAP plugin uses v3.0.0 of the Google Billing library. (I believe this should be easy to just update.)
Regarding consent SDK (part of Mobile Advert plugin) there has been a lot of changes here, the one which is part of the Scirra Mobile Advert is classified as "Deprecated", and is actually marked with a red warning text on the Google dev pages that is is deprecated and is no longer even maintained, at all. It does not comply with the actual regulations and should not be used. Google has released their UMP SDK a long time ago, which is the one to use now.
Regarding Admob SDK (also part of the Mobile Advert plugin) Google has made a lot of changes for the different ads, most of which was released in v19.2-19.7. Even if your plugin has used the latest SDK you have not updated to the latest methods. It was in the release of v20 that Google finally removed the old deprecated ads, which basically made the Mobile Advert to fail totally..
Google had released documentation how to prepare for the v20 update, which was obviously not implemented by Scirra.
To state that your use of any of these three SDKs are "up-to-date" is just not correct.
(Edit: And there has been just as many changes for the iOS SDKs as for the Android ones mentioned above)