Problem here is that Guance is not judged on the same objective standards as others. I would say that a player like Granlund is having a bad season to date. And most seem to agree.
But Granlund has almost identical face off % (both around 40 %) the same number of hits (although Gaunce in less games) and a slightly better Corsi rating (CF%) . On top of that Granlaud actually has some goals and points and about twice as many shots as Gaunce.
Well yeah, Granlund is considered a better player.
The issue here is that you are prioritizing one "objective standard" over all other objective standards. Gaunce is a low scoring player. Everyone has acknowledged this. The disagreement is: Is a low scoring player still useful at the NHL level?
For the people that value possession (objective standard), he's useful. As a fringe player facing heavy QoC, that buys him time. Does it absolve him from scoring though, IMO, no. He still has to score to have any NHL longevity. For now though, his non-points based work is enough to keep him in this line-up. Agree/Disagree?
Is Gaunce ok defensively. Yes he is ok but nothing special. He is not the re-emergence of Bob Gainey and certainly people saying he a one of the top defensive forwards in the NHL is an extreme exaggeration. If he had that reputation he would be great demand at the trade deadline. That would be great but unfortunately is untrue.
Rather than dispute your assertion that Gaunce is merely "ok" defensively, how do you rate his defensive ability relative to his teammates? If he's not one of the best, in your opinion, then you will face disagreement. He's getting increased TOI for exactly this reason. And if you acknowledge that, then you've kind of acknowledged why he's still on the roster...