I work at a company who's entire business was written in stored procedures and it has been a massive source of complexity and pain for us. Here are my issues with it:

- Most web languages have a wealth of tools for testing, introspection and instrumentation that don't exist or are hacks in PL/SQL. Unit tests, basic logging, aspects that log function execution time, posting to error tracking & app metrics services, etc.

- PL/SQL is not expressive or concise. String processing, in particular, is a nightmare. This means more code, buggier code & thus reduced developer happiness.

- At scale, developers need to be parsimonious with joins in the data layer, otherwise partitioning is impossible. This is technically possible in PL/SQL, but runs completely against the grain of SQL, so I can't imagine this actually happening in the real world. This is probably my company's biggest source of technical debt.

- SQLPlus doesn't return a non-zero error code when certain errors happen when installing PL/SQL, so release scripts have to install then assert the user_errror table is empty. This is just ugly.