'Weak and pathetic': why is the EU not using its leverage to stop Israel?

For the same reason the US is not using it. Their extensive lobbying enforced by terabytes of compromising data and kilometers of compromising documents. Countries are being hijacked one by one by a populist oligarch, then things go easy. Many Russian and post-Communist oligarchs found shelter in Israel which increases their sophistication even further.

EU politicians are indeed "weak". Their term of office is four years-ish. They want career afterwards. They want real estate. They want their kids to study and live in expensive EU cities. They really don't care what political decisions it takes to achieve all these.