Don't get me wrong I didn't like Marston in the last game either which was one of my problems with it. still I don't find Arthur to be likable at all yet. Just seems like a typical bland character that will go around doing everyone's errands.
It's not like John Marston or the GTA V protagonists where their morality and overall persona is fully established regardless of what the player does. Like they all had tons of dialogue in trailers, especially the GTA V ones. By comparison, Arthur's barely spoken at all in RDR 2's marketing.
I could be wrong and Arthur is meant to be a blank slate and quiet, but that feels very un-Rockstar.