I don't know if all the blame goes to postgres or not, but a unit test in Rails is typically what others would call an integration test and Rails' architecture

I don't know if all the blame goes to postgres or not, but a unit test in Rails is typically what others would call an integration test and Rails' architecture is more to blame than SQL. If someone chooses to use postgres in their application, don't be surprised when you see code that uses postgres. Wanting to force others to make applications that work with the lowest-common denominator of SQL could make one appear naive, and that you might not have ever faced the same problems others developers have faced.