Reading your first sentence, I was prepared to answer with "well you must have never had a truly great manager who cared about you as a person and helped you grow", but you revealed that later.

It's one of those Pareto principle things. I had 4 terrible managers, but my 5th one helped me grow in ways I wouldn't have alone, and taught me lessons I still carry today. There's no measuring an effective manager.

The ones that do it because it's a job or because they were Peter principled into the role eventually work themselves out of the role, thankfully (or at least out of the company).