I think the reason no one really brings it up because shortened is so vague, and I don't really know how shortened you can consider it since she runs a war for five years and clearly wasn't rushing to take over the other two kingdoms since her primary offensives don't actually start until after Byleth comes back.
Her war does ultimately make the continent become better, at a pretty high cost that may or may not have been necessary and I'd lean towards arguing it was not. My main problem is really just how much of a hypocrite she is at the end of the day though, she's pretty much the same person as Rhea when it comes to their methods. Crush your enemies, love those who do everything you tell them, obsess over Byleth (I guess Sothis in Rhea's case), condone inhumane experiments for the sake of getting what they want. But it's part of what I like about her as a character, people tend to be hypocritical and I think it's fun to have her holier than thou attitude be unjustified because it's better than having her be like "har har har I'm evil" instead.
As for why I argue her war wasn't the best course of action, it's because the game has a really strong theme about the characters making mistakes, bad decisions, or succumbing to their fatal flaws. The corrector of their fatal flaws that stops them from losing their life because of it ends up being Byleth though, who helps set them on a better path in their respective stories. I don't know Claude's yet, but I understand Rhea repents somewhat on her path and realizes she was wrong, Dimitri recovers from his insanity on his, and Edelgard does not become completely corrupted by power by the end of her route. So it only goes to fit that her decision to declare the war was an incorrect choice because it was made by her fatal flaw, that being a hubris that she has to do everything herself by any means necessary.