You are begging the question still. Citation needed.
> In the Russia-vs-Ukraine war there are relatively few dead children because the demographics of both counties skews towards adults — not because of the military doctrine of either side. Children make up less than 20% of the population and hence less than 20% of the civilian deaths.
That dog won't hunt. ~58k Ukranian soldiers killed + 12k civilians = 70k total [1]. 633 Ukrainian children killed [2]. 20% of the population is children but they make up < 1% or those directly killed in the conflict. You will probably take issue with the degree of urbanisation etc., but it was your example.
> Fifty percent of civilian deaths are children not because Israel is targeting children (as if they were cartoon villains!)
I suggest you are strawmanning the argument here — I don't think Israel is actively targeting children is an accurate representation of the concerned 'side' overall (I'm sure you can find a tweet making it). But it is plain their actions are pretty indiscriminate wrt the combatant:civilian kill ratio.
> they just a normal amount of evil.
You haven't supported this claim, and its a considerable leap from 'Gaza has a pyramid-shaped age structure'. Yet, there is data available on recent urbanised conflicts and what the 'normal amount' is.
[1] https://en.wikipedia.org/wiki/Casualties_of_the_Russo-Ukrain...
[2] https://www.savethechildren.org.au/media/media-releases/chil...