Postgres is amazing, but there are some issues you quickly hit with systems like this:
1. Side effects: Want to send an email when something happens
2. conditional permissions: Need access to data under certain circumstances not modelled by the security language?
3. Subset access: Access to parts of the row / document.
4. Aggregate access: Access to eg. a count of rows you can not access.
These are usually solved using serverless functions – or an API written in code.
Personally I err to the side of just writing some code, maybe because I enjoy that part of the project. Then I might be more inclined to use no-code solutions for the frontend, where others want the freedom and flexibility.