Here is the demographic breakdown by age and gender, showing a rough bell curve heavily favoring males in their late teens, 20s and 30s.
Here is the total casualties compared with Gaza's demographics.
If IDF actions were "indiscriminate," these two sets of data would track closely together. As you can see...they don't.
Keep in mind that these statistics include many people who were killed by Hamas rockets that fell short or secondary explosions from booby trapped houses and the like. The victims of those are far more likely to reflect a distribution in line with the demographics, so a very high percentage of those killed by Hamas actions would be children.
If anyone actually objectively researched the actual number of deaths that can be attributed to the IDF - a highly unlikely scenario in Gaza - then the difference between the demographics and actual dead in Gaza would be even more striking.