Urgh, yes... Fanon!WWX with his insecurities and apparent low self-esteem… Who doesn't like to burden people with his troubles and thinks he doesn't deserve to be loved or receive help from anyone. Literally the EXACT opposite of the canon WWX we know and love 😅
I can't help but wonder if this pervasive misinterpretation stems from other adaptations. Perhaps some viewers who started with the CQL or the donghua before diving into the novel might be projecting a skewed impression onto canon!WWX, misinterpreting his actions through that lens. Of course, I know a lot of people who have come from the CQL and have an excellent understanding of the novel and its differences. It's as though some enjoyed the wacky, chaotic, suicidal dummy of the CQL so much and simply see what they want to when reading the novel instead 😅 I usually find the ones who claim he's the above are usually the same people who think WWX is "stupid," despite him being an undeniable prodigy!
Or, perhaps it really is just a genuine misinterpretation of his actions. Yes, at the beginning of the novel, WWX sometimes leans into the whole "I'm so bad and evil" persona he's been given, but that's his sense of humor shining through! He's not genuinely self-loathing; he's mocking those absurd assumptions about him. It's his personal joke, a very "WWX" way of laughing at the absurdity of it all rather than dwelling on the unfairness.
By the time he's reincarnated, I'd argue he's much less "bitter" and more at peace with his past. He's learned from it, which is why he no longer seeks revenge. We see him save everyone during the second siege, despite many of them having been present at the first siege that brought about his demise and still wish him dead a second time around! While he certainly experienced some bitterness in his first life, contributing to his mental breakdown and subsequent demise, his return in MXY's body shows a character who has processed much of that.
Sometimes, I really do wonder if people simply cannot grasp WHY WWX does what he does. This is of course the majority, but I know from first-hand experience while debating over this very mischaracterisation with some in the fandom that this really does seem to be the case... These people have outright declared they would not have done what WWX did, they would not have saved the Wen remnants or tried to help anyone else in need. And while some people might not act similarly, whether from fear or lack of confidence, it's unfair to trivialise WWX's just and heroic actions merely to excuse their own shortcomings.
It's like they can't understand why he'd jump in to help people or do what's right despite the inevitable backlash. So, instead of trying to fathom such selflessness, they justify their own lack of understanding by claiming he has "self-esteem issues." They'd rather assign him that flaw than acknowledge their own differing morals.
It's almost like people would rather say he doesn't value his own life (when we canonically SEE he does, when he declares he's about to drop Su She if no one will help him...) or feel he deserves love/affection/help (despite us seeing him readily jump at the chance of these things, if offered) than feel bad about their own lack of morals or admit their favourite side character just never offered him any help in the first place!
It's actually rather hilarious because WWX isn't the only person to jump in and save someone either... LWJ and JZX both did this (LWJ more than once) and no one ever claims they have low self-worth 🙄 And at least WWX usually has a plan whenever he does so... LWJ and JZX protected Mianmian without any means to defend themselves. They were only saved because WWX devised a plan in a dire moment.
The beauty of WWX's character is he doesn't dwell on things. He has the ability to focus on the little joys in life and adopt a positive outlook. So although he is obviously affected by all the tragedy and hardship around him, he quickly picks himself up and bounces back. Even finding himself in a strange, new body that isn't his own… he has a little moment when he sees the unfamiliar reflection looking back at him and thinks of the past and then pulls himself together. WWX doesn't spend too much time overthinking such negative things. He acknowledges it and moves on.
I do feel this is often misinterpreted as him being flippant and not caring about the suffering and unfairness he's faced - which is of course not the case. I guess it could be considered a coping mechanism… and it probably is to a certain extent. That, mixed with a personal philosophy influenced by his parents, cultural beliefs and teachings. Regardless, I don't think it's an unhealthy approach, nor does it stem from a "lack of self-worth”.
I think the "self-deprecating" label often comes from misinterpreting his sense of humour. He pokes fun at himself, his circumstances, or his infamy, but it's always in good-natured jest. Given his confident personality and positive attitude, this should be more than apparent. But if you've already misjudged him as someone with low self-worth, then his little jokes can indeed take on a much darker tone.
As you rightly say, WWX doesn't regret his actions—and he has no reason to! Even when he thought his efforts were for nothing and every single Wen remnant had been unjustly murdered, he still believed he did the right thing and would do so again… because he possesses an unwavering, strong sense of right and wrong. This makes the revelation that Wen Yuan survived all the more poignant. It made no difference to his belief that it was the right thing to do... But it offered a tangible, living testament to the goodness he fought for.
As you touched on yourself - WWX embodies the Jiang Clan motto through his unwavering commitment to doing what is right, even when the odds are stacked impossibly against him and the entire world has seemingly turned its back on him. He consistently "attempts the impossible" (or a more literal meaning of the motto courtesy of doufudanshi "do what you know you cannot") by literally doing what he knows he cannot... striving to uphold true justice and compassion in a world that often lacks both.
It really is a shame people can't just appreciate canon!WWX for what he truly is—a character who is steadfast, morally absolute, and stands by his principles, regardless of how difficult that path might be to follow ❤️