That's because the US is already providing them weapons. Israel is pragmatic, if we stop selling them weapons they will go to russia or china and either of them will be super happy to provide since having an ally in that area is really useful.
Look, you can speculate that they'd be exactly as capable without US support all you like. But the fact is, the government of Israel has decided it needs international & domestic support, and that pushing it beyond breaking point must be avoided. Hence a piecemeal, plausible-deniability approach.
Governments-- even authoritarian and repressive ones-- require the acquiescence of their people and the world at large. And so, when they pursue their worst impulses, they will dress it up, or hire it, or go slowly and deny its happening.
Because I would expect some numbers closer to their numbers if this was a genocide. Like at least 10% of the population by now.
So you
are using one of the worst genocides in modern history as a benchmark, and concluding that if this doesn't approach it, it cannot be ethnic cleansing. Can you not see how utterly inane that is? Plus, the Rwandan genocide
led directly to the fall of the government perpetrating it. So obviously more cautious powers will avoid emulating it.
Besides which, we've already established that ethnic cleansing isn't simply about absolute numbers dead. The population of Gaza has reduced by 6%.