I'm not going to question your experience or your analysis about the activities people do, and whether or not they are actually helpful. You have consistently demonstrated that your judgment is sound and reliable.
Thanks for that . . . I wish I could tell myself the same thing and believe it.
However, speaking as a teacher, I would say that there's nothing wrong with drills.
To be clear: I'm not saying that drills are a problem in themselves. My personal and thus limited experience is that you can drill specific actions, and sometimes sequences of actions, in response to predictable stimuli, but that it's harder to drill anything in response to a totally inconstant, transitory environment, and that it's for all practical purposes impossible to drill complex, composite skills made up of indeterminate numbers of responses to indeterminate numbers of stimuli (by which I mean something like "physics" or "medicine").
In the specific context of tango, I think you absolutely
can drill, say, 180° right pivots on the left foot, or back steps with the right leg, or lapiz technique. You can probably drill, for instance, ochos, though they're composite movements with huge variability – even "left ocho atras" leaves open questions of starting point, degree of pivot, speed, suspension, and exit. Still, any of that might be useful. But you can't drill dancing all 2:56 of
El flete except as a choreo that won't work with anybody but one specific partner in an open space, much less on other music. And you can't drill even the pivots or ochos very usefully with a partner – that's best done by yourself in front of a mirror or at a barre.
What worries me is when people say they did couples drills of specific steps to specific music with specific partners, because my (very) personal experience is that such things hurt more than they help. You need to drill by yourself to perfect movements, then "just dance" with someone else to integrate those. Until you do the second part, you aren't dancing.