I adore this game so much !
Like you wrote OP, I remember very well the negative vibes the game was giving off. I was even thinking of cancelling my preorder of the special edition as the game, developed by Koei Tecmo, felt like a high school anime.
And then the leak happened and there was a glimmer of hope. What was leaked promised a much, much more interesting narrative than what I was expecting. When the E3 2019 direct dropped, I did the biggest 180, from suspicion to complete hype. And boy did the game deliver.
The game is not perfect and clearly suffers from being too ambitious with too little development time. There is so much map recycling and the graphics, apart form the character models, are pretty damn ugly. 3 out of 4 stories also sadly follow a very similar template. But damn I don't think I have ever been so fixated and passionate about a cast of characters and a story as Three Houses. Rhea, all three Lords, and so many others like Dedue, Dorothea, Petra, Hubert, Ferdinand, Lysithea, Annette, Jeritza, etc are all such good characters. The cast and the story really delves into important and fascinating topics such as the consequences of trauma, reform vs revolution, the place of organized religion in society, tradition, xenophobia etc.
I started with the Black Eagles and went the Crimson Flower path and after finishing it, I immediately started my Verdant Wind playthrough. After 4 months and 400 hours, I completed all 4 stories. The real stand out for me was Edelgard who ended up being one of the most intriguing characters in all gaming for me.