Actually, to me, that is incredibly powerful. I can't really evaluate Zuckerberg's effectiveness, but you can't fix problems if you can't admit fault, and many in leadership positions never admit fault.
"I'm sorry, it won't happen this time" is what abusive relationships are made of.
https://www.youtube.com/watch?v=Q4zd7X98eOs
Do people find this sincere? It seems fake/manipulative and too convenient. Facebook has been doing this for a decade+.
Which is where you might be confused, you can be incredibly insincere and abusive (seems common in business) but still a great leader (great in this context not meaning just), as they've shown they can a) get out of sticky situations b) continue making money and c) have a relatively happy team. So in this scenario what would actually back up your argument would be demonstrations of the apologies having zero impact, the team hating the apologies and thus being less productive, and/or a general loss of revenue.
I'd be more inclined to agree if it wasn't working so well for him.