Legally untenable as in - see my first post on this thread - the assertion that "if Israel wanted to commit genocide it would have done so already" [paraphrased] ignores the entire history of what has and has not been deemed genocide and how and why. Either via formal legal findings or by scientific consensus.
A legal finding of genocide just doesn't require "everyone being dead in minimum time". The actual legal requirement is that some act or acts were carried out with the specific intent of destroying in whole or in part a group as a group. The legal threshold here is extremely high in that it requires the so-called dolus specialis (specific intent). This is why, in the case of the Yugoslav wars, only the isolated case of Srebrenica was eventually found to legally constitute genocide. And Serbia as a state only guilty of "failing to prevent" rather than perpetrating.
A more social science or Lemkin based reading is far broader and would (and does), using the same example, characterise genocide as any action(s) designed to destroy a group as a group.
My core point being, once again, "but everyone wasn't exterminated already" is not an argument against something being genocide. Not even in the legal sense.
Notably: I think we can all agree that Nazi Germany, as a state, committed genocide?! We might want to debate over whether it was one or several (i.e. one per group) but not the general consensus.
Legally? There has never been a finding/verdict that said Nazi Germany committed genocide!