I had situation where was implementing something quite simple - an URL shortener. I didn't use PostgREST, but I decided to use ORM, because it was simple CRUD operation. It had an option to either use generated url or allow user to specify a custom one. And it worked as expected.
But then once completed I decided to add extra functionality, for example extra statistics, like what IPs were accessing it and how much. Adding expiration times etc.
I realized that ORM encouraged me to implement all of my logic in the application even when I actually would put less load on the database and made things simpler if I would let the database do many things for me and use types and functionality provided to me. I am not taking here about using stored procedures, I could do all operations as 1 at most 2 SQL statements. While ORM had to send multiple. In the end I dropped SQLAlchemy (this was python code) and just use psycopg2 directly didn't even bother with wrappers, just used built-in pools. It was also easier for me to make my code use two endpoints for reading and writing, so I can scale my code better.
I realized that ORM did not save me much code at all, it was the same amount of code with or without it, and without ORM I had greater control of what I wanted to do.
I previously believed that ORM was standing in a way when your application gets bigger, but my belief was ORM was good for small projects. Here I realized that it doesn't bring much benefits even for simple projects.
I think REST interface like this is doubling down on what ORM tries to do. Maybe it could be beneficial in places that don't have libraries to communicate with a database and only can make http requests?