The thing about trying to evaluate or analyze characters like 3H lords is that the narrative primarily frames them morally and personally/emotionally, but if you treat the in-universe logic seriously then you have to look at them institutionally, and the institutional incentives generally run orthogonal to the moral concerns and are often not particularly relatable to normal people who do not hold the kind of power politicians do.
Like these characters are heads of states, and states are generally amoral and self-interested. Sometimes the morally correct thing happens to intersect with those interests, but that's generally not the main driving principle, and politicians often have incentives to greatly exaggerate the moral dimensions.
Edelgard wants to end hereditary Crest-based nobility -> because the Empire is a bureaucratic state that doesn't have Relics = aren't reliant on Relics for military purposes anyway so they can feasibly do that. Is a war on Central Church 100% necessary if your main goal is soley internal meritocratic reforms? Probably not. Is it easier to gain executive control if you can invoke wartime emergency powers and easier to rally domestic support if you invoke imperial primacy and reunification of lost territories and accuse Church of laundering imperial decline? Hell yes. Does allying with Agarthans and giving them a chance to entrench themselves in the wartime apparatus a good idea? Probably not. Is it less embarrassing and project the impression of a strong empire better than explaining to other factions that the Empire is so compromised that wartime emergency powers are basically the only way the emperor can have any real authority? Yes.
Dimitri wants to find the conspirators behind Tragedy and restore Duscur -> because fundamentally all of that was a state capacity issue and that would eventually have to be addressed regardless of the moral dimension. Was genocide on Duscur morally wrong? Yes. Was it also an embarrassing demonstration of how little control the crown exercised over its own nobles/how much they lacked a monopoly on violence? Also yes. Would restoration of Duscur be morally correct? Yes. Would that be the exact kind of project that both demonstrates and lets him consolidate the power to ensure his own elites can't just kill him over disagreements? Yes. Was it morally/ethically wrong for him to torture and kill suspects out of vengeance? Probably. Could he have gotten away with being vengeful if he just tortured and killed the suspects in dungeons where nobody else could see and get alienated? Also yes.
Claude wants to open borders and allow freer movement of people and ideas -> Leicester is highly mercantile and the only country sharing land borders with a non-FΓ³dlani country that's confirmed to be massive, powerful, and probably wealthy (Sreng is notably resource poor). Would this result in less prejudices and problems for people like him? Yes. Would Leicester and Almyra be the ones primarily making a fortune off of all the trade back and forth? Also yes. Would Claude sympathize with Brigid/Duscur/Sreng issues on principle? Probably. Would he have a good reason to prioritize those above a myriad of other stuff unless Leicester or Almyra gain something by helping them? Probably not. Does Leicester and Claude have reasons to ally with any of the other factions depending on the situation? Absolutely. Does that mean they'd actually give a flying fuck about whatever political/ideological conflict over legitimacy the whole Empire-Church-Kingdom issue revolves around or that allying one of them means eternal loyalty and commitment to anyone else's cause? Fuck no.
In other words, from an institutional perspective the the correct rational answer characters like lords would give to most moral criticisms of them would be "you might be right but that's your problem, not my institution's."
Would the moral criticisms still be valid? Yeah. Would objectively correct moral criticism without any other accompanying pressures/consequences deter a political leader from pursuing institutional interests because they suddenly had an epiphany about how morally wrong their ways were? No.
Because the thing about epiphanies is that they usually occur after the person has gotten into deep shit and faced undeniable/overhwhelmingly negative consequences (and somehow survived). People who are doing something morally bad and getting what they want out of it, or at least do not feel the negative consequences as directly, tend to not have those epiphanies. And power tends to insulate you from consequences, or at least you only pay the consequences after everyone else has.
So personally I think debates that are like "what this powerful character does is wrong and harming people and they are a morally bad person vs no it's not they're actually making things better and they're a morally good person" don't actually do much to help understand/explain these types of characters.
"How does this character's power work (source/extent/what's required to maintain it) and what does that let them get away with," in my opinion, tends to explain more.