I think YG was the outcast from the beginning, giving him the "introvert" role and the sleeping stone one. I actually think that behind all he is intelligent and very ambicious. He probably is treated badly due to his lack of desire to be part of this bullshit... But i havent watched them a lot so i dunno, this is more intuition than anything...
I Think YG and TH were always not liked by the other members
But with TH they know they need him because he is a stan atractor and most fans like his visuals
YG to be honest, I think he is pretty useless in the group right now, especially with bt-s new music that don't use the rap line so much, at least jhope is main dancer and RM oficial english speaker. But what does YG do?
maybe that break he took for his shoulder was actually him thinking about staying in the group or not
but he is also very obsessed with charts and awards so he probably stays for that alone