Seconding the wisdom shared by u/julienreszka and you.
Stuff like schemas and data dictionaries and reuse are chinese finger traps for us geeks. Exquisite problems we can't look away from.
I eventually decided to treat most data ingestion (ETL) as screen scraping. Honoring Postel's Law. Pull out the interesting relevant bits as needed. Ignore the rest.
There's still an internal model, natch. But it's the smallest, most obvious model to support my immediate use cases. Nothing more.
See also his talk https://www.youtube.com/watch?v=ujMgQqp8YSY