If Israel wants to take that position, they’ll need to denounce the Nuremberg trials. “Crimes against humanity” were invented for them, as the Holocaust was legal under German law (https://en.wikipedia.org/wiki/F%C3%BChrerprinzip).

As the article indicates, prohibitions against perfidy and other war crimes predate the Conventions.

(And I’d note that, as occupying power, Israel is subject to other requirements.)

(And if this is truly your argument, “Hamas doesn’t have to follow the rules either” is the logical conclusion. Which makes whining about their uniforms a bit odd; there is no scenario where "Hamas has to follow the Conventions, but Israel does not" is a coherent position.)