Hi, I hope its okay when I reply with my own perspectives? As we already were able to keep things somewhat civilized?
First off I would say, its very obvious looking at the state of discourse that you're not the only one (but you at least don't make entire posts trying to frame Edelgard as some sexual seductress, lol. That person exists!), but I think its also more of a you issue. Not in that you do something wrong, but that Edelgard and her route are simply not for you, because as is clear with the large popularilty Edelgard enjoys, thats not the experience all people have with Crimson Flower. In the end, its a game about different perspectives and values and chosing your side when those ultimately come to a clash. It would be boring if this doesn't spark discourse and fundamentally different perspectives of what is right and whats wrong. For all of its flaws, the fact that 3 Houses sparks this amount of Discourse even years after its release is a testament to what it does right.
For example my perspective in all of this, when I played the game on Crimson Flower Route first, was that I came to broadly agree with Edelgards point of view during Part 1. She shares alot of her perspectives during it and as I saw early on, how the entire social structure of Fodlan is heavily inspired by the three estates of the realm feudal structure of medieval europe, I was naturally inclined to by sympathetic towards her viewpoints, as I will usually prefer to side against feudalism in a narrative that allows and encourages me to do so. I got bad vibes from Rhea from the start and tended to believe Jeralt, who as the father of my character I was prone to believe, in not trusting her, especially since very early on, we see more of the oppressive and tyranical nature of the church and the evils of the crest system. In my personal first playthrough, I came to suspect that the Flame Emperor is more nuanced than it appears at first, while Rhea became more and more creepy after Sothis awakening, so when it came to the holy tomb, I did a leap of faith and trusted in Edelgard, as I agreed that the church must be destroyed.
For me, the reactions towards Rheas turn in Crimson Flower feel very similar to the outrage people expressed in the recent Elden Ring DLC, when a certain character as was expected didn't turn out to be as noble as they would have assumed, because by that point they were set in their headcanons of him being a benevolent and purely good figure. Rhea in Crimson Flower is consistent. She is consistent with the bloodthirsty side of hers we saw during the games first cutscene and her cruel and vengeful attitude whenever somebody challenges her during White Clouds. Silver Snow is textually not a validation of Rhea as we saw her in part 1, what it does is offering a potential redemption for her under the condition that Byleth forms an especially strong bond with her. She herself admits her wrongdoings and expresses guilt in the following S-Support. What Crimson Flower shows is that at this stage of the story, Rheas love and adoration for Byleth is conditional, as not long before she literally tried to mind erase them to revive Sothis in full, and that Rhea is prone to immediately devalueing and dehumanizing them if they disobey her. After all, at this point Byleth hasn't even taken arms against Rhea, they are just standing against outright killing their student. I would also say that for me personally, Rheas entire demeanor during part 1 comes off heavily like grooming and love bombing, which is why I personally tend to dislike her.
When it comes to Arianrhod, I personally tond like this part of the story. For me it is one of the flaws in it, as it is left without any lasting consequences, and feels very much like the writers just forcefully inserting it into it to remind us of TWSITD still being there and inform Crimson Flower players of the Javelines of light. What I will say is, that it is not the only such forced inclusion just for the sake of it. I can see the rationale of Edelgard though. Edelgard took a gamble with killing Cornelia in Arianrhod and was punished by it for Thales and reacting to it prematurely would them losing momentum and the Kingdom successfully launching a counter offensive, as well as further interventions by TWSITD if she openly revolts against them now, so she has to lure Thales for the moment into a false sense of security, that she falls back in line again. I don't like it, but I will also say that if thats the dealbreaker, then the route probably wasn't for one to begin with.
When it comes to Dimitri and Edelgard, the whole 'must you continue to kill' exchange is quite a mistranslation compared to the original text, where Edelgards point is to ask him if he will be satisfied, once he takes back, tramples back. This changes the entire context of the exchange honestly:
Though I will also say, I don't have personal issues with this exchange myself, as, what most people leave out, its followed by Edelgard also expressing her determination that she will not stop and do everything necessary to creat a new future for Fodlan. Initially I also took the line as Edelgard being sassy which I'm like...okay with? I'm a feminist, I like it when the queer female lead doesn't owes your typical male protagonist turned villain respect and in crimson Flower, Dimitri himself dragged his Kingdom into war by siding with the church and for the sake of Dimitris delusional desire for vengeance. Which is, again, delusional. Dimitri rants and blames Edelgard for things she had no control over and which she didn't do. He is completely obsessive over her and she has the right to be apalled by him. Again, as a feminist, I like that. She doesn't owe a guy who obsessed over her and wants to brutally murder her any respect, he himself is the one who chose to throw away any semblance of dignity he had.
I would also say that other people will feel as you do towards Rhea and Dimitri. With Rhea I already laid it out why I don't get why people love her so much and consider her heroic and good. With Dimitri, I was initially kinda excited to play Blue Lions after CF. Dimitri was, ultimately, a cool villain in my opinion, I liked his Post Timeskip Design more than his Pre-Timeskip one and I wanted to see where his route leads into and whats his perspective is. I ended up not liking it. Like, I played it before I went into all this discourse with high hopes and I just ended up not liking it or him. He seems very flat to me, with people conflating a character focussed story and a character going through a a redemption arc with deep storytelling, when for me it just seemed comical how he jumps in personality, especially when he just immediately snaps from somebody who sadistically glees like he's some dark isekai self-insert about torturing a man and then immediately jumps into being the enlightened and redeemed savior king. I didn't like how afterwards there were zero consequences for his actions. The parley also didn't sold me, it seemed for me like him engaging in ad hominems and framing him as morally superior because he got people who carry him, it had some very unfortunate implications of how abusers irl might act. Ultimately, I also found his whole position rather pessimistic and miserable, that humans can't rise above themselves when they are given the opportunity and that they should be kept reliant because its safe. Thats how he came off to me. Many of his scenes also come off to me like trauma dumping and him being somewhat self-centered, only relating to others by making them fit into his personal perspective.
If thats not your experience, I will not argue that. If you love him and consider him a great and touching character, all the more power to you. Same with Rhea. This wasn't meant to convince you of my perspective, but to lay it out to show you, how I experiences the game and its characters in a fundamentally different way than you did. I personally would love it more, if I totally stoked by Azure Moon, I would love it if I had ended up loving and cherishing every single route equally, I paid money for and invested time into that game after all. But thats not the case and for me personally, Edelgard just resonated the most and I feel similarily to Rhea and Dimitri as you do towards Edelgard.