Thanks, but it's something else. When I say people shove their data into other teams' DBs, I really mean into other teams' schemas... and they don't even have direct SQL access to their data anymore, rather the teams set up some CRUD API which they have to painfully maintain.

We aren't using Postgres but a more specialized DBMS. Everyone basically does the first thing in your example, sharing one cluster. The real issue is it's a big corp with red tape around stuff, people don't want responsibilities like compliance, and people are rightfully scared of keeping things performant on a fancy DBMS. Our team isn't scared, we did it, but it wasn't easy either.