[Solved]-Why is gunicorn_django not recommended anymore?

The essential part of gunicorn_django, wsgi.py, became integrated in Django itself.

To quote an already existing answer:

Starting with Django 1.4, your project will already have a wsgi.py, which can be used with any wsgi server (of which there are many, gunicorn being just one).

Essentially the old Django integration for gunicorn was just a convenience to get you up and running faster, but it’s no longer necessary because all Django projects now have wsgi.py.

UPDATE

First of all, in Gunicorn 18.0 gunicorn_django became deprecated.

Second, since the first writing of this answer I have personally encountered obscure errors that
were specific to gunicorn_django in conjunction with --settings command line parameter (gunicorn command and ./manage.py runserver worked fine).

Namely, the obscure import error application.some_model: 'field' has a relation with model another_application.AnotherModel, which has either not been installed or is abstract.

So, no, I would not recommend you using gunicorn_django in your new projects.