> Luhmann is still one of the most cited, grappled-with and thought-about sociologist across a number of disciplines.

Unfortunately (though I think this is a regional thing also - Luhmann's still pretty strong in Europe, especially in Germany where "systems theory" has become synonymous with Luhmann's systems theory, but not so much in the USA, I think).

One of the problems with Luhmann stems directly from his Zettelkasten: His tendency to tear citations out of their original contexts and name drop witnesses for his own point of views where the original text did not support his view at all.

You can see the system at work actually: He truly made a lot of stuff his own in ways never intended by the original authors - boon and bane at same time.