> but I'd rather learn SQL than whatever custom-flavor-of-ORM-query-language some ORM tool created

This point is worth emphasizing!

When you application carries non-trivial business logic, it will create non-trivial DB access patterns.

The developer will either use SQL or some other language that, pragmatically speaking, translates to SQL. But either way, they will learn some DB expression.

I'd rather use a standard. Existing familiarity, easier to find docs, support, and is probably more bug-free, etc.