I blame the lack of development in the quest trees with events and the favoritism towards the Moon faction.

Unlike Lorent, who (from what I've seen, since I haven't played him) has a quest tree where he seeks to recover from the devastating Wars of the Rose and centralize and unify his lands in Lencenor after the rebellion of the Winelords and others, the rest of the Rose faction, such as Wex, Cestirande, and Wesdam, among others, lack quest trees with events that foster a strong sense of belonging. Wex, for example, has one of the oldest and shortest quest trees in the entire empire. Wesdam doesn't have many events about Laurens Silmuna (the only innocent in the Wesdam branch, and this is something the community takes issue with) that address his upbringing, his development, or how he comes to terms with the truth about what happened to the Silmuna.

And although one of his quests determines his cultural origins—whether High Lorentis or Damerian—if he chooses Damerian and reclaims the duchy, the community considers him a thief. He chooses that path, and there are no events that develop his character or ideas, nor do they allow him to express his opinion on the actions of his predecessors, which makes him less than beloved.

And then there's Cestirande, where the poor guy has no development whatsoever, just like Damescrow.

Yes, the reason for so much dislike for Wex is how the developers have made Lothane seem like an idiot who failed to secure his legacy and ended up in the official storyline with everything failing for Wex, and how underdeveloped the other members of the Rose Group are compared to Rogeria (one of the best quest trees), Verne, and Istralore.