My absolute favorite video discussing the narrative and game structure is from Noah Caldwell-Gervais. It's very long and exhaustive, but I find it to be incredibly interesting and on point.
(RDR 2 starts at 1:42:00)
highly recommend anyone wanting to hear someone talk about digital cowboys for a few hours give it a listen. It's real good.
I basically disagree with all criticisms in the OP, I tihnk the game has perfect pacing for what it is going for, and I think that character flaws are not the same as bad writing. Arthur goes along with Dutch because he considers himse a father figure, and feels like he owes him, not because he thinks that Dutch is right.
RDR 2's side missions are also super important to really get the full picture of Arthur as a character. Only doing main missions kinda hides his true self. He doesn't shoot up or rob towns to pass time, that's merely his "job", an extension of Dutch's will. When you do side missions, it's all Arthur's own curiousity or willingness to help. There is really only a few side missions where you get in shootouts with humans, it's always either self defense or defending a friend.
Arthur's journal is really an incredible mechanic because it canonizes everything you do in the world. From main missions to just observing animals or checking out a creepy looking cabin across meeting characters in side missions... it all gets penned down. When you finish the game and look back, it's an incredible journey.
Arthur's redemption doesn't really happen while he's alive, and he fully knows that he is not a good person. Every time people tell him that he immediately denies it or visibly gets flustered. His redemption is through John and his family, everything he does in Ch6 is to ensure that they have an opportunity to start over as better people. And in the epilogues you get to play it out. John fucks it up by disobeying Arthur and going for a meaningless revenge, but outside of that, Arthur very much succeeds.
I think people often overlook that the game is about a gang of low life criminals who pretend to be more than that thanks to Dutch's cult-like leadership. They all have fucked up morals and aren't particularly bright. So questioning things like "Why does Strauss get kicked out but actual murderes don't" is just kinda weird to me. In thecontext, it makes perfect sense. Arthur learned about his TB, which he figured out was indirectly caused by Strauss, and Strauss once again sent him on a collection run to collect from helpless people.... he reached a breaking point and kicked his ass, that is all.
As for the public perception of RDR 2, I think you are trying a bit too hard to justify your not liking the game as much as you hoped/expected OP. It sold 35 mil copies, won well over 100 GOTY awards, literally won steam's GOTY last year which was entirely user voted, gets constantly discussed to this day... the game is easily one of the best games of the last generation. The big "fall off" you keep mentioning just isn't there.