How many times haven’t I seen applications logging onto the Oracle database as the schema owner. This is definitely not good practice. And usually by the time the DBA discovers this, it’s “to late” to change. I’ve heard managers say: “It will be to expensive and to much of a risk changing this now”. (Note! The same manager actually argued the same when I asked them to – at least – change the password to something else than the username.)
The best way to actually change this is to talk to and educate your developers. In my company I created a script the developers could use when creating new schema users. The script is meant as a template, and should of course be changed if needed.