Part of the trouble is Israel can't prove the 12,000, and no one actually believes the Hamas figures are legitimate. But there are not better figures available for either number. So 1:1 for Gaza is the best we can estimate.
The wikipedia article should be read as a starting point in understanding how extremely unreliable those numbers are, and how much it depend on how people define combatant and civilian.
So, as horrific as this war has been, I don't think the claim that this is "one of the the deadliest wars for civilians in general" holds up.
I don't think that is a true statement. Obviously it is bad for civilians in any war, but there are other conficts that have been much worse.
That's not actually true. The ratio is similar to other wars. Civilians die in war, they die a lot. War sucks. But Gaza is not unusually deadly compared to other wars.
In any case Israel is not conducting a war, they are conducting a massacre.
While the initial cause for war is obviously different, that does not justify war crimes.
I don't think western-brained folks realise how bad this looks to the rest of the world. For example to India, and the amount damage it does to the West's reputation.