> but if you have a db that is accessed by various systems written in Java, dotnet, erlang or whatever else I suspect the smooth sailing of Django can run into headwinds quickly

Only if those systems are constantly adding/removing tables and columns. And adding isn't a problem, Django just ignores what's not specified in the models.

Django does have default table and column names based on the models that it prefers, but all of it is overridable in officially-supported ways. We're using it with mysql databases originally made for VB6 and C++ with inconsistent naming schemes that aren't even close to Django's defaults, that nowadays are also accessed by perl, php, and python. Most of our python uses are daemons that only use the models and none of the rest of the web framework - the models are defined in a common library they all use.