Hello:
Do not give up yet.
IMHO, there may be some misinterpretation of XML Element structure as errors here:
Code:
https://www.fsdeveloper.com/forum/threads/official-airport-to-sdk-project-here-is-a-small-app-to-help-you-draft.450344/post-931755
As for the error in this post:
Code:
https://www.fsdeveloper.com/forum/threads/official-airport-to-sdk-project-here-is-a-small-app-to-help-you-draft.450344/post-931759
...that 'may' be a 'status' error due to ARP2PROJ not (initially) finding the actual path to an airport.
Be aware that Asobo changed the folder location of generic airports to distinguish them from newer "World Hub" designated airports in the \Official folder chain.
It is likely that now anyone can eventually find- and access- a MSFS default airport ( due to de-compilers

).
If you tell us which airport ICAO you are looking for, we are likely able to help you- and ARP2PROJ- find it.
GaryGB