I believe the idea is that the best language for any given situation will vary depending on the situation.

The point, I guess, is that Python isn't really optimal at anything but is very good at a lot of things.

Realistically, there are enough software fields that Python just isn't applicable for this to be taken with a pinch of salt. However, as a language, it does have quite a large sweet spot: easy to pick up, expressive, integrates well with low level languages for heavy lifting and almost perl quantities of libraries.

IMO its popularity is justified although I'm not a fan myself.

It depends on the context. The joke is that everything has a most optimal language and Python is never the most optimal language- but it has got breadth.