And Java Justice For All
For the same reason a carpenter does not use one tool for his job, companies should not rely on one tool for development of systems. There is nothing wrong with PL/SQL when used for the correct jobs. We use it for ETL and reporting on our warehouses, together with other BI tools. We also use C++ if we need to manipulate huge amounts of data in memory (on the server) and then persist changes or write the results as text or html reports.

For OLTP (you say "production") we use java together with frameworks such as Spring and Hibernate (and JDBC) to make communication with Oracle easier.  You should then investigate your middle tier because you need efficient connection pooling for production - we find that Weblogic is stable for this.  Your architect is correct to mention inserts and simple selects if your OLTP consists of mainly transactional tables, but nowadays "OLTP" systems are complex and hybrid and Oracle has to manage a wide range of DML, concurrency and locking strategies.  If you have the luxury of designing OLTP from scratch, keep it simple and clean.

You can find a full list of development tools here.