Now if a given exercise, for example barbell hack squats, work well for a given person then the last thing I'd do is disparage the exercise for that person. That would be stupid.
But speaking in general, when a once-common exercise slowly fades away over the decades and by now is done by rather few, even more rarely among those succeeding at high levels, and where those who do do the exercise generally do so because of having read about it (and not in an article about what top lifters are doing, but in an article that's reaching for unusual things), generally there is a reason for the exercise fading away. I.e., it just is not needed.
In the case of barbell hack squats not working well for you, I just wouldn't worry about it.