But in Hushed Whispers, you reset things so that those people still exist. They still had the chance to go out and fall in love and have children. They get another chance.
And what number of deaths stands to be okay? A few hundred? a few thousand? What's acceptable? Thedas needs to change sure, but it's the change that people like Cassandra and Dorian enact. It's the slow change of good people fighting for what's right, pushing against the corruption. I am struggling to think of any point in history where good was ever achieved by the mass destruction of life.
It comes down to his talks with Varric and Sera where he tells them that they're not what they "should" be. What he's really saying is that they're not what he thinks they should be. For all we know, Varric's perfectly content to be himself, to be cut from the stone and it's his opinion that matters, not Solas's. Sera's the same.
It's an interesting debate with regards to morality. For me, I just think that no amount of good can justify the deaths of others to achieve it. There's no acceptable losses. Maybe I'm idealistic. Maybe the current world mood has me brooding on things a little too much. while i'd like to see what a collapsed veil would bring to Thedas, I my Pc's would be on the supportive end of it.
But what changes? What's changed for the Elves over the past thousand years, really? They get helped by Andraste, then taken down again by the Exalted March of the Dales. They get helped (possibly) by the Hero of Ferelden, but nothing comes of it beyond some temporary, localised improvements in Denerim's alienage. Attempts at rebellion in TME are crushed by Celene. The Inquisitor may try to help, is there really hope that such change will be permanent this time? How many thousands, or hundreds of thousands have died waiting for this slow change that never seems to materialise or crushed by the authorities that oppose it? Why is the slow drip-drip death of a people inherently less tragic than the quicker, more violent deaths of the same number? It seems to me it's just easier to ignore if people are dying quietly waiting for something to happen.
Same with mages - don't the trespasser end slides indicate that the chantry reforms are stalled or getting bogged down or whatever? Aren't the circles back, only two years after a war that saw Mages and Templars tearing each other apart? How many more young mages have to be put through a brutal Harrowing before they stop being seen as the universal boogyman?
In real terms, what about the American Revolution? The English Civil War, which led to the beginnings of parliamentary democracy (worldwide, I believe)? The French Revolution? The American Civil War? Horrible violence, many deaths and trauma, yet effecting change that ultimately benefited more than it hurt.
And In Hushed Whispers, those same people don't necessarily exist - from the children who were born in that year (to couples who never meet without those specific circumstances), to those who are effectively different people because we are formed by our experiences.
I agree, an interesting moral debate! I can see why anyone prefers slow change, it's my own instinct too fwiw, but I can also see why people can gravitate to sudden, violent change that forces an issue to the forefront, particularly when said people have been subjugated for a hellishly long time.
Edit: Again, not agreeing with the mass bloodshed potential in Solas's plan, but I think different points of view are worth exploring nonetheless 