This article was well balanced. I find title just a bit misleading, since "What ORMs have taught me: just learn SQL", to me, carries a slightly different message than "What ORMs have taught me: learn SQL".
The second sentence is a little more compatible with the first line, "they can be used to nicely augment working with SQL in a program, but they should not replace it."
That's certainly how I use them. ORMs can save you a lot of irritating typing where it comes to insert and update statements. Aside from that, I write a lot of raw SQL.
I have seen what I would describe as ORM-induced, yaml-induced database damage. This isn't meant as a criticism of these tools per se, they're perfectly compatible with a well designed app. But I have noticed that people sometimes create databases that are useful only in the context of their configuration-file/ORM heavy app. Essentially, the programmers conceive of their data as a set of objects, and they use the config file to store global constants and the ORM to persist files, almost as if they're pickling and retrieving objects back into the system.
The result is a database that can't really be queried with SQL, more or less useless outside the context of the application. I firmly agree with developers who maintain that information will outlive an application, a database will outlive the software that was originally designed to use it (perhaps in parallel with it). I think a SQL database should be useful all on its own as a data source. If you got rid of the app, you'd lose a lot of operations on that data, a lot of UI, a lot of valuable things, but you'd be able to get at and use your data. If that's not the case, I'd seriously reconsider the design.
Kind of hard to do that without understanding SQL, so yeah, definitely learn it.