What exactly is the grievance against Son Heung-min?

No matter how much I think about it, I cannot understand the '96 line (players born in 1996).
I am curious as to what their grievances against Son Heung-min are, considering they seem to think they are
taking the lead by speaking out.
A thought suddenly occurred to me;
inferring from what Hong Myung-bo said to Son during the World Cup,
I wonder if they are displeased with him acting as captain and talking to them about tactics
and playstyle, even though he isn't the manager.
The players apparently told Hong about this, and Hong was also displeased, which is why he was excluded from the South Africa match.
Or perhaps they simply dislike how a captain should act,
or there is a massive gap in their perspectives regarding leadership.
Between the interview boycott and everything else, it just looks like they dislike him from top to bottom and refuse to listen.
It is truly unfortunate. I wish Son could hold out a bit longer, at least until the '96 line passes and the next generation
establishes itself. It must be mentally very difficult, but I hope he stays strong.