I like how I get downvoted just for asking for a source. That article has mixed feelings about the reliability of the 20k estimate, but even if it’s only half that, it’s a lot of dead civilians.
The problem faced by the IDF is in fighting an insurgent force that deliberately embeds itself into the civilian population of a very densely-populated area with shoddy building quality. There’s basically no way to fight Hamas without innocent Palestinians getting caught in the crossfire. I do think Israel has made its point and am glad that most of the world is pushing for a ceasefire now.