with intent to destroy, in whole or in part, a national, ethnical, racial or religious group

This part matters a lot. If we ignore it, anyone killing any member of any group can be said to commit a genocide. Showing this is typically quite difficult in court cases, because it's pretty hard to read someone's mind, and very few people are stupid or arrogant enough to announce such intentions.

Israeli officials are either so stupid or arrogant, going around saying stuff like "kill them, kill their mothers, kill their children", "It’s an entire nation out there that is responsible. ... This rhetoric about civilians not aware, not involved, it’s absolutely not true.", “If we don’t give them food, they will move...”, and so on. And please don't underestimate this "and so on". There's pages and pages of Israeli officials basically saying "we're committing genocide".

Normally it takes years of investigative work after the fact to even get a peep out of the ICJ, but here they conceded that Israel is plausibly committing a genocide about 4 months in. That's huge. And a key part of that is the fact that South Africa showed Israel's intent. And that's just something we haven't done for Russia's actions yet. Russia's illegal invasion of Ukraine has been going on for years, and there's no plausible genocide ICJ ruling against Russia, and not for lack of trying. The evidence of intent has as of yet not been found.

Article II

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:

1. Killing members of the group;
2. Causing serious bodily or mental harm to members of the group;
3. Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
4. Imposing measures intended to prevent births within the group;
5. Forcibly transferring children of the group to another group.

See the fifth part where the Russians stripped Ukrainian children of their nationality, forced Russia nationality on them and forcibly adopted them to Russians.

https://www.un.org/en/genocide-prevention/definition