I don't think there's injustice and mistreatment like solos keep claiming, but there is most definitely a pecking order in BTS.

For one thing, consider that Jimin began training at BH almost a full year after Taehyung but debuted as main dancer and lead vocalist while Taehyung debuted as vocalist (some people would say sub-vocalist but that is a term with no meaning). Of course Jimin is hugely talented as a dancer, but this doesn't take away from the fact that Taehyung wasn't seen to be equally valuable by the company. Then, Taehyung's visuals are seen prominently but when it comes to interviews or documentaries, he often is incidental or occurs in combination with someone else. He's a strange combination of promoted and sidelined at the same time.

Next is Jin. It is rare that an event spotlights Jin - this documentary showed more of him for the first time. I don't know how to feel about the Bangtan Bomb being released showing JK and Jimin covering his songs once the news came out about Moon being ranked so high. It's nice to see that BTS likes his song but it was also his moment in the sun overlaid by Jimin and JK. While this might seem like overrection, you can often see Jin / Taehyung moments in documentaries being overlaid with Jimin or Jungkook's commentary - they are primary lens from which BTS content is to be consumed.

Also, I know the teasing of Jin is all in good spirit and they love him but his flaws are openly discussed a lot more than anyone else's, and his marketing is definitely less exuberant than a lot of others.

J-hope also doesn't get the spotlight as frequently. I'd leave mixtapes out of it because that is work done on personal time. He is frequently present in documentary content but sometimes I feel his marketing is somewhat lukewarm. He definitely does a lot more for his own image than the company does.

RM and Suga have a lot of power in the group, but Suga has had tracks rejected by BH lately, and his production hasn't featured much on recent albums. While RM continues to figure prominently as a lyricist.

People like RM and Suga are a lot more confident speaking for the group than Jin or J-hope, who often keep comments centred on themselves. Jin especially is quite hesitant - his nervousness is apparent during the disbandment speech, and sajaegi speech where he glanced to RM for support. ML doesn't take charge usually but Taehyung is constantly looking to a member for validation - of course, he isn't the greatest at public speaking, but it's also as if he isn't called to be more representative for the group etc.

Mind you, I don't think any of this is mistreatment, it's strategy and member personalities and dynamics also factor into it. But it definitely is there!