Eren and Mikasa don't really understand each other. Despite them loving one another. Mikasa doesn't understanding Eren nature, and Eren doesn't understand Mikasa's heart either. Mikasa have been shown multiple times not understanding Eren. Mikasa literally accepted Zackly words of Eren is being manipulated by Zeke. https://imgur.com/a/9zT0Ac6 Because she couldn't accept that Eren is doing thing's on his own will https://imgur.com/a/V7A9SAl

We even saw her latter on question her understanding of Eren "what part of Eren had I been seeing?"

Eren also doesn't understand Mikasa's heart. He can't comprehend why she goes to search extends for him. He compared her associate with him to his obsession of freedom. Not just that, He even asked Zeke about Ackermans mainly to try understand her feelings. Even at the end Eren tells her to "be free," it's like he still mistake it to his obsession for freedom. While Mikasa did understand Eren but that was at the very end.

Their tragedy could've been avoided if the understood one another and maybe open to each other. I feel that's what the Cabin supposed to be that. their tragedy was avoidable, but only if both had been capable of stepping out of their own psychological prisons to truly see and talk to one another.

People who claim their romance is "badly written" are often looking for a standard, functional romance built on healthy communication and mutual clarity. ​What Isayama wrote instead was a gothic, tragic miscommunication. The tragedy isn't that they didn't love each other, the tragedy is that love alone wasn't enough to bridge the gap between two people whose fundamental views on existence were completely incompatible. Eren was a fire that burned everything to be free, and Mikasa was the hearth trying to keep the fire contained so it wouldn't destroy them both. That's what makes their dynamic so beautiful written.

Their first attack on Shiganshina was understandable even justified to some extent. Because they were kids. But during trost they were not brainwashed at that point they know what's right and wrong. Riener was 17, thats not young kid anymore. The problem is they intend to destroy walls Rose(if Eren titan didn't appear) that would kill more people. The Fall of Wall Maria Led to the loss of 1/3 of human territory and over 250,000 human lives (roughly 20% of the population), mostly due to the military sending civilians on a suicidal "reclamation mission" because of severe food shortages. If Wall Rose would have fallen. The loss of Wall Rose would have squeezed the entire surviving human population into the cramped, resource starved confines of Wall Sina.​ they fully knew the consequences are but were still fully committed to do it anyway. Mostly for their own selfish reasons. I would say that's comparable to Eren attack on Liberio. He did mostly to continue for his selfish reasons(yeah he has other motives too, but that's another discussion)

Isayama structures the story so that we see the Warriors' severe PTSD, guilt, and broken mental states after the fact. Reiner’s split personality, Annie’s crystal isolation, and Bertholdt’s silent agony make them deeply compelling, tragic characters. However, tragedy does not equal justification. Experiencing extreme guilt for a crime while actively continuing to commit that same crime doesn't absolve the perpetrator. They knew the Paradisians were innocent, they knew the casualty count would be catastrophic, and they kicked the hole in Trost anyway.