> I am not saying that it is impossible.
And I am saying far from impossible, it's quite convenient. If I am using rails, I will plugin devise, couple it with can-can and be done with authorization and authentication. Django makes enough assumptions about the user model, but not enough to warrant not using it for a CMS system. Django flat pages is a small CMS system, but in practice is useful only when the developers are creating/editing content. If it meets my requirement, I sure as hell will add admin & flat-pages apps, do minor tweaks and call it a day.
I don't see how any of it is a hindrance.
> But merely pointing out that Python web framework ecosystem is rich enough that many of its hundreds of frameworks are possible options.
I didn't contend Python ecosystem isn't rich enough. I am merely pointing out that "Django or Rails is not suitable for writing a CMS" is not true. A CMS can be as simple or as complex as you want, but the average CMS is the simplest kind of web application. Rails and Django make the task easier, not harder, and Django came out of a newsroom CMS.