But you can decouple the database logic from the app logic anyway, without using stored procedures. They don't actually help you do this since you still need code that knows what stored procedures to call. Also, I'm not sure how this makes security easier? It seems like security would be the same or maybe a little harder since you now have to track the stored procedures you're currently using as well.

I'm not really sure what you mean by "you can deploy schema changes independently" and "you can change everything and the app should not notice". The stored procedures are basically just an extension of the apps logic right? So you can deploy them at any time, sure, but that isn't different from an app that doesn't use stored procedures, because you could also deploy changes to any part of that app at any time.

I do think stored procedures can be more efficient, because you have a lot more control. But it's not like they are clearly superior from an organizational standpoint. If you write an ORM using stored procedures, it's still an ORM.