The main reason to use an ORM is for programmer efficiency. Sure I can write a bunch of CRUD operations but why bother if I can have the ORM do it for me? Since CRUD operations are either inserting a new row or accessing/updating by a primary key it'll be indexed as well so no perf issues[2]. The additional work by your app code for the ORM library is meaningless compared to the DB round trip anyway. My favorite part? Adding a new field goes straight to the model and nowhere else[3].
The big place for raw SQL is as the secret sauce on the meat and potatoes of your apps. Once you've got a real data set and you want to combine, slice, dice, you're not going to do that through an ORM. You want those queries to be as performant as possible. If you've structured your tables properly (proper foreign keys, normalization, etc) then the writing custom SQL will also be much more straightforward then trying to kludge together ORM commands to do what you want. On top of that, the work will happen on the database where it can filter it prior to your app processing it.
For our app[4] most of the CRUD pages are handled by an ORM but there's quite a bit of custom SQL too. One example is for security authorizations. Validating security authorizations (can user X access DB y) is a hierarchical check. The logic is all done in a Postgres stored proc (well technically a function). Doing it via an ORM would inefficient, both in programmer time and computer runtime.
[1]: You probably should though. It's generally a good idea to have some kind of white listing for what is an acceptable value for a field. Either way though you need to make sure you escape them when outputing HTML for webapps to prevent XSS. That combined with prepared statements when interacting with user inputs is the only right way to do things.
[2]: For basic CRUD operations and even simple one-to-many lists. Beyond that things can and do get hairy but those aren't the majority of cases. The majority of app code is vanilla id-based select, inserts, updates, and deletes.