I think whether the world is "broken" is a subjective quality for most people. I don't believe most of the people and civilization of the current world could exist without the Veil and (if he's friends with the Inquisitor) Solas doesn't pretend his plan makes the world objectively better, just better for his people.
Since creating the world with the Veil was an enormously destructive event, it stands to reason undoing it might be equally destructive. For all we know, it can only be done in a way that resembles opening the Eye of Terror. I mean it's not like we know enough to conclude that cannot or should not possibly be the case.
And even if it can be Veil can be destroyed without a destructive effect like that, it's definitely going to release some destructive beings, even not counting all the demons and spirits that will be free to interact with all the unprepared mortals, the Evanuris are probably going to be so pissed that I expect them to start smashing every single thing there is to smash out of spite.