I so much agree that praising ability instead of effort is a mistake.

However, a word like "lazy" is a bit tricky. While you are saying "stop being lazy" (meaning - please cease the behavior you are exhibiting in this moment) it can have an undertone of "you are lazy", especially if repeated over the course of days/months/years.

I wonder if there is a better phrasing to respond in a scenario like a kid not searching for his own backpack. Maybe "Do the work!"