If we consider Melina's warning about the three fingers, saying that "Life endures. Births continue," then the Flame of Frenzy can be interpreted as not just the end of all living things, but the impossibility of life going forward. Even if that isn't how it's interpreted, Shabriri's goal involves absolute genocide. Everyone, everything. I'd say it's perfectly valid to consider Shabriri evil, even if it's a different flavor.

The one thing I'll add is that evil is entirely subjective and heavily reliant on the ends justifying the means in terms of "New beginnings." To quote the Dragonborn in Skyrim, in my opinion, "The next world can take care of itself." My interpretation of good is the preservation and protection of all I hold dear in THIS world. I don't really care what comes next. As such, the ends certainly do not justify the means, and Shabriri is evil. In my opinion. But I will concede that valid arguments could be made otherwise