"Both sides, X and Y, are bad" requires as a prerequisite that X is in the set of "bad". Doesn't matter which of X and Y are government policies in Israel or Palestine.
Now, if the comment you'd replied to was saying "it's all X's fault, Y is innocent", then "we've all seen Israel's true face now" would be a reasonable response.
Fair enough, I'm getting into the weeds a bit and left some things unsaid.
What I'm referring to is a rhetorical technique deployed to get people to simmer down and accept the status quo. Folks who support Israel know they can't get people to be 100% behind Israel anymore, so the fallback position is "it's complicated, the Palestinians don't seem like great people either so I'm not going to go out of my way to support them". That leaves the ruling class foreign policy establishment to run the horror show the way they like without any troublesome democratic meddling.
If you want to see an example from a historical genocide, just look at what the Turkish government writes about the Armenian genocide.
> "it's complicated, the Palestinians don't seem like great people either so I'm not going to go out of my way to support them"
People are complicated, anyone saying otherwise is also selling you propaganda.
Hamas in this case (and I do mean Hamas not Palestinians in general) were explicitly genocidal, mellowed a bit, and are currently back using explicitly genocidal goals.
Hamas were just fine with targeting civilians, have been for ages. Hamas are also weak, which is the biggest difference between them and the IDF. That power disparity makes it easy and obviously necessary to condemn the big strong force that's damaged or destroyed approximately all buildings in Gaza, and killed 2-14% of the population depending on whose estimate you follow. Some governments (e.g. Germany) do still find they need to say "well Hamas started it!", but overwhelmingly the international consensus is "I don't care who started it, we need to stop it".
This "complication" or messiness is real, but the implication is the opposite it is claimed to have. That it makes further civilian violence on either side more understandable, or less easy to judge.
Both countries fomented war for decades. On civilians.
Israel by tacitly/actively letting Israeli citizens illegally "settle" land that was not theirs, and the violence, theft and worse those settlers imposed on Palestinian civilians.
Those actions would be considered acts of war, if done against any stronger actor.
And Hamas fomented war with its responses and atrocities against Israeli civilians.
But this "complication" is of a kind that makes it even more egregious for either side to claim any moral high ground for continued harm to the other side's civilians. Making genocidal type starvation of an entire territory's civilian population even less acceptable. If that is even possible.
"Both sides, X and Y, are bad" requires as a prerequisite that X is in the set of "bad". Doesn't matter which of X and Y are government policies in Israel or Palestine.
Now, if the comment you'd replied to was saying "it's all X's fault, Y is innocent", then "we've all seen Israel's true face now" would be a reasonable response.