There is certainly a danger of being overly concerned about grammar on one side and not caring enough about grammar on the other. Duolingo (mentioned by several) is an example of this second kind. An example of the first kind is when a student wants to know ever detail of a sentence when we're trying to learn common phrases, or illustrate a different point.
<ul><li>Why is it <em>dir</em> in Wie geht es dir?</li><li>Why is it Gut<em>en</em> Tag, but Gut<em>e</em> Nacht?</li></ul>
Or while explaining accusative, the student wants to know how to say "I drink the coffee with my mother" and asks:
<ul><li>Why is it meiner Mutter? (Ich trinke den Kaffee mit meiner Mutter.)</li></ul>
There are often simple answers, but there are appropriate times to "play" with the language or to focus on single elements - such las learning basic phrases or direct objects -- and trust that the rest will make sense later. Where I disagree with your presentation in the article, however, is the suggestion that worrying about endings is a "waste of time".
I suspect that we fundamentally agree - and that it's bad to worry <em>too much</em> about endings - but how much is too much and how much is enough is often a balancing act - and subjective.