My complaint may be less about this exact graph, as used in the article I linked, but more about the fact that I've seen this same graph in a bunch of places, and I've never really seen it mentioned what exactly the graph shows.

Personally I find it sort of suspect to compare "productivity", which is the average economic output per unit of time worked for all workers, then compares it to the average wage for the subset of workers. Particularly since productivity is usually presented in the layman's understanding of the word, which would imply that individual people are more productive, but are not being paid any more, but that is not what this graph is showing.

I feel like a better label for this chart is "economic growth is disproportionally going to the managerial/capital class", which is a thing that can be said without invoking productivity.