In my experience any system that is bigger then a demo raw SQL is the perfect abstraction unless you need to support multiple database types, which many systems

In my experience any system that is bigger then a demo raw SQL is the perfect abstraction unless you need to support multiple database types, which many systems do not. Complex queries are much harder to read in Ecto then SQL. You need to understand SQL anyways. I like working in and building systems using AyeSQL that allow you to compile SQL to functions. So use Ecto for the easy stuff, if you want, but the complex queries stick to SQL. It is already the perfect abstraction.