In reality things are, unfortunately, complicated.
A central reason why genocide is so special is because it could call for UN intervention. Therefore, the UN definition is of some importance, which goes as follows:
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
a) Killing members of the group;
b) Causing serious bodily or mental harm to members of the group;
c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
d) Imposing measures intended to prevent births within the group;
e) Forcibly transferring children of the group to another group
Notice that according to the UN, the murder of political groups is not considered genocide. The Genocide convention was signed in 1948, and Stalin was not too keen on not being kept from killing political opponents. You could of course still argue political mass violence to be genocide, it just isn't according to the convention.
There are perhaps two more interesting points that stand out. One is that the likelihood of success is not observed: merely the intention. The lunatic in the US killing a Palestinian child and wounding his mother was genocidal, as his intention was to kill Palestinians in order to rid them off the earth. It doesn't so much matter that one mentally deranged person with a knife is unlikely to have much success in the task.
Intent causes a further problem, which is of course why the UN is not going to intervene in Israel: It's very easy to hide your intentions. There are certainly members of Hamas who speak (or spoke) openly of removing the nation of Israel off the face of the earth, and you could therefore relatively easily label their actions as genocidal before the ICC if necessary.
With Israel it is, of course, more complicated. They are certainly using collective punishment, murdering civilians and children at an extremely high rate. However, they will insist that the intention is not to destroy the national group that is Palestinians: Most of them will argue that that the intention is to fight off Hamas, and that civilian casualties are just an unfortunate side effect of any war, even if just. Some lunatics will claim that they cannot kill off Palestinians as a nationality because Palestine never existed in the first place. The latter group would likely be less successful in the Hague.
If Israel can reasonably claim that their intention is not to destroy a group of people according to the convention, they will always be able to claim it is not a genocide and be at least technically correct.
There are two main implications as far as I'm concerned:
The UN will stand by and do nothing as civilians are murdered, just like it always does.
Legally, genocide is not a particularly fruitful term to throw about when discussing an ongoing conflict. Targeting civilians in murderous massacres is always deplorable. Endlessly arguing whether or not it formally fits the definition of genocide matters when the UN is considering intervention, but it is hardly relevant when considering whether or not war crimes are okay. These actions are despicable and should be forcefully protested, independently of whether they can be proven to meet the high bar of genocide.