It doesn't. Mosul's civilian population were Iraqi citizens, the conflict was much larger, lasted a lot longer, used smaller munitions, resulted in a lot more military deaths and significantly less civilian deaths. This is despite the enemy being significantly better trained, better equipped, better logistics, years of preparation and less intelligence by the anti-ISIL coalition.

The issue in this case is (possible) genocide, which is a different question.

"Better" is hard to judge, but mosul was about ten months and resulted in 10k civilian deaths. This one is already several times that count in a much shorter time span.

Historical comparisons aren't relevant when evaluating whether conduct today is acceptable, especially when we're talking about the deaths of innocents.

Every day is an opportunity to be better than our ancestors.

Peace is usually a product of avoiding "whataboutism". Humans of all shades and beliefs and origins have proven time and time again how barbaric we can be. True "justice" can probably only happen with the extinction of our species; to avoid that, someone has to say "enough" even if there are those who believe it isn't.