"can be spoken poorly and still be understood"

That is only something that is easy for native speakers, though. The points a non-native speaker anchors in the speaking flow are completely different to the ones a native speaker does, and depend on the mother language, making the thousand "official" variations of native English quite a challenge.

I find far superior other languages approach of having a "high" form taught in schools that everybody native is supposed the speak and understand, and the dialects are left for home.